What should I do?

[#1]

We've been with Plus.net now for about 3 years and in all that time I've got nothing but good things to say for them. I've had to contact them twice in the past regarding our phone line going dead and each time they had the problem sorted within days. The first time a Open Reach guy was here within 30 minutes. The problems turned out to be a loose connection in the local cabinet. Didn't effect the fibre broadband, which stayed sock solid just like it has since day one, just the phone side of things.
Now...... at the moment we've out of contract with plus.net and are currently on the old Fibre extra 250gb package + £5 plus addon. We only use between 150-200gb per month and with the plus addon we get very fast speeds any time of the day. I could save £5 per month by either removing the addon or moving over to the unlimited package, but even though i've no intention of moving to a different company I don't want to be tied into a 18month contract.
What would you suggest?. I can't remember what it was like before the addon. I normally do my downloading, streaming and gaming on a Sunday and during the week in the evenings.
I'm I right in thinking that the new unlimited package would give me the same connection speeds has the £5 addon..
Would plus net remove the 18 month contract tie in if I ask them nicely?

[#2]

The new unlimited package has the £5 pm Pro add-on as an option, but shouldn't be needed. Nothing is slowed down at any time and downloads will run at line speed if that is all the connection is being used for. However if interactive traffic (such as streaming and gaming) runs alongside P2P or Usenet downloads the streaming and gaming content will be given priority. Users would normally regard this as beneficial.
But the implications of changing package are complex. Having you phone line with Plusnet removes one of the complications with current pricing but I think will still involve changing to current phone service pricing. Do you pay line rental monthly or use Line Rental Saver? And do you pay for Anytime calls?
I think your best option would be to give the Customer Options Team a ring (0800 432 0200 or 0345 140 0200 Mon-Fri 9:00am to 8pm, Sat 9:00am to 5:30pm) and see what they can offer. Some tie in is probably inevitable but I suggest seeing if you can get a discount in exchange for that.