Welcome to the forums...its always great to see a new member!
Plusnet have recently announced that they will be working with Easynet, an LLU operator to acheive higher speeds to customers where possible.
The speed upgrades from BT are not LLU, but rather MaxDSL - where your line will sync up to the maximum stable speed possible.
If you are only on a 1mb connection now, this may be due to your current line statistics, unfortunately the advent of newer technologies is unlikely to bring with it speeds of anything more than about 3.5/4mb on those lines.
I am in the same boat, a longer line and a 1mb tops speed with BT for now. LLU providers such as easynet base the speed on a different set of criteria than BT, and as such I could expect maybe 3.5mb on my line.
Sadly until new lines or vastly improved technology, our ilk are not likely to see speeds of beyond 4mb any time soon.
Out of interest do you know your line statistics (downstream attenuation and Signal to noise ratio) ?