Moving from Tesco to Plusnet (maybe) - Number Porting Problem

[#1]

A long time ago I had a telephone line with Telewest, who eventually became Virgin Media.  I'm talking 1991 here.
We moved house and changed to a BT line, porting our number to the new property, on a different exchange.
3 years ago we moved locally, so still on the same exchange and moved the number, still with BT, to the new house.
In sept 2012 I joined Tesco for both Home Phone and unlimited broadband.  There was a bit of a problem during the setup in that we lost incoming calls for a while, and the BB service has been spotty to say the least, hence my desire to get away from Tesco.
I chose Plusnet on the basis of their Which? Customer Service rating, and placed the order on 22 November 2013.  Went through the number and postcode checker, and all was accepted.  No indication that we could not port the number - didn't expect a problem as we're not moving house and OFCOM regulations say if you're staying on the same exchange and the line is still live then the old provider (Tesco) must release the line & number.
There have been several attempts to place the simultaneous (phone + BB) move with Tesco and each time the order keeps getting rejected.
The latest info from Plusnet is that their supplier (Openreach) say:

Quote

As we have discussed, I am very sorry that we are unable to keep your telephone number. We have requested this several times and after I have spoken with the Number Porting department of our Suppliers and they have advised we are unable to keep your telephone number as it is under the jurisdiction of Virgin.

Now to my mind, this is absolute boo-hockey!  The number has not been under the control of Virgin since 1991, and has been with copper wire providers since that date.
However, I duly phoned Virgin to be told exactly that - they have no interest nor control over that number.  I phoned Tesco who could see the attempts made to take the service, but deny that they have been blocking the switch-over.
Does this make any sense to anybody?
To me it sounds like Openreach is playing silly b**gers, as the number has been successfully ported twice before, and we're not even asking to move exchanges.
I've asked Plusnet to try to get a comprehensive technical reason for this, but the most I've had from Plusnet so far is that each provide is allocated a range of numbers it can use and that unfortunately they can't use ours.  This has to be c**p - how would you ever know if a number can be ported to a new supplier without going halfway down the transfer process before finding out - that's just ridiculous.
Your comments please, ladies and gents ...

[#2]

it depends if you out of contact with tesco if you are try and complain to http://consumers.ofcom.org.uk/tell-us/telecoms/changing-provider/ then they have to release the number to plusnet i will say complain to ofcom if it gets rejected.
Contact your provider’s customer services department and explain your problem.
If this doesn’t resolve the issue, make a formal complaint to the company. You should find details of how to do this on the back of your bill, on their website or ask their customer services.
If your provider is unable to resolve your complaint, ask for a deadlock letter. This enables you to take your complaint to an Alternative Dispute Resolution (ADR) scheme. 
ADRs act as an independent middleman and will examine the case from both sides and reach a decision they think fair. If eight weeks have passed since you first formally complained you can contact the ADR directly.
There are two ADR schemes – Ombudsman Services: Communications, and the Communications and Internet Services Adjudication Scheme (CISAS). All service providers must belong to one of the schemes.
Your provider will tell you which scheme it is a member of, or you can use our ADR checker.
try them both
i looked which one they are under it is http://www.ombudsman-services.org/communications.html thats what tesco is under

[#3]

Thanks for your input.
I am out of contract with Tesco and have liaised with them all along regarding my move.  If you re-read my initial post you will see that I have queried with them the rejections and they have categorically stated that any rejection problems have not come from them.  The rejection is a from Openreach to Plusnet - but nobody knows why ...

[#4]

it not should be like that i was with bt before and virgin they should accept the order and do it in my words

[#5]

Hi, I've asked one of our provisioning team to look into this for you. It's looking a bit more complicated because Tesco have you on an LLU service (which I believe is actually run by TalkTalk) so not sure if that's where the complication is, but the order to port the number is being rejected because apparently it's already been ported? We'll let you know as soon as we find out more.

[#6]

Hi Matt & thanks for the input
Have to admit I'm confused:  LLU?  Isn't that where both phone and broadband are bundled?  But we knew this from the start.
No idea where Talk Talk come into it, as they have never been mentioned before.  Presumably Tesco are just repackaging/reselling Talk Talk services?
"already been ported?" - which occasion are they talking about?  1991 from telewest to BT at a new address/exchange, 2001 from BT to BT at a new address or 2012 from BT to Tesco at same address/exchange.  They can't think it's already been ported on this order, surely, as the Tesco line is still live and kicking.
Your further advices eagerly anticipated.

[#7]

Hi,
LLU is basically where other companies either install their own equipment in BT exchanges or rent the equipment directly from BT, and yes you're entirely correct about TalkTalk - Tesco are indeed reselling their services, as are the Post Office I believe.
Not sure where the already ported comes into it though I suspect it's from back when you moved the number from Virgin to BT in the first place - that's the only occasion where it could have been stopped I believe, as the number was originally allocated to Virgin in the first place (rather than being moved to them from BT).
I can see the agent I talked to has raised a ticket on your account and is keeping it as a personal ticket with herself, so she'll keep you updated that way and make sure it all goes through fine. Hope that's helped.

[#8]

I remain optimistic, although it was kept as a personal ticket previously with no real progress.  Was told it had been to the number Porting Team and could go no further.
Let's see if this latest request goes through without rejection.