Question on "Current Speed" v "Estimated Speed"

[#1]

Hi Guys.
My broadband connection speeds (according to plusnet) are as follows.
Estimated line speed:
26Mb (Download speed could vary depending on line conditions. Estimates are the maximum speeds that your phone line can support. These speeds are dependent on the package you choose.) - Checked on 2014-10-13 11:58:05
Current line speed:
77.4 Mb
I'm on the 40/20 package, and pretty much get that in speed tests - 37 Down, 18 Up at quiet times.
My question is, would my speed rise up to the 77.4Mb if I were to go for the full package? If so, why is the estimate so low?
Cheers,
Lee.

[#2]

Estimated speed is not relevant
The Current Line Speed should say 40Mbps but doesn't and hence I don't understand how you are limited
The only way you can check to see what you get is the BT speedtest Further diagnostics which will give the IP profile but going by your upload speed result you may well get a significant increase on the extra package
What does this say http://dslchecker.bt.com/

[#3]

Well, I definitely shouldn't be on the full package (too tight for that), so just assumed I was correctly being limited by Plusnet to 40/20 (despite what current line speed says). I know that on the first day of fibre, the current line speed reported by PlusNet was actually "40Mb" on the dot. It only changed to 77.4 a few days later.
When the engineer installed fibre, she did say that I was syncing at pretty much the best speed possible (80/20?). This suprised me, as the the BT Broadband Availability Checker always had my estimates down much lower (see below). Note I am about 300 metres away from the new fibre cabinet, and so was always a bit disappointed at my estimated speeds.
This is why I ask the question. Am I syncing at pretty much full speed, and will see an increase if I upgrade the package? Or is the BT estimate correct, and I'll see no increase?
FTTC Range A (Clean) 35.1 26.3 7.6 6 -- Available
FTTC Range B (Impacted) 27.9 15 7.2 3.9 -- Available

WBC ADSL 2+ Up to 2 -- 1 to 3.5 Available
ADSL Max Up to 1.5 -- 1 to 2.5 Available
WBC Fixed Rate 2 -- -- Available
Fixed Rate 2 -- -- Available
Other Offerings
Fibre Multicast -- -- -- Available
Copper Multicast -- -- -- Available
When the engineer turned up, she said I pretty much got the full

[#4]

Hi BigLee,
I've check into your account and corrected the profile for you (it should now say 40Mbit not 77).
You are syncing at 80Mbit though, and should you want to swap product, we'll happily do that for you.
Tony

[#5]

BTO Estimates are really just that a guess on what they think your capable of you never really know until you are connected and running as a number of factors could either increase or decrease what you get.
for example my estimate when i got FTTC back in March was 67Mb when i was up and running i synced at 65Mb which was great,  i got a line fault back in June which saw my sync drop to 57Mb even with the fault fixed i never got my full speed back, also my estimate was cut by BTO to 38Mb so more than half of my initial Estimate was removed even though i'm still synced well over that.
problem with them doing that is should i go else where my estimate being now only 38mb i wouldn't get offered the 80 / 20 product even though i can clearly obtain and sync at that level.