Evidently you need rather longer to think about it than I originally thought...

If you get FTTC available then SKY Fibre Unlimited would seem to fit your requirements.
To quote:

Sky Fibre Unlimited is a residential service that offers totally unlimited usage - there is no fair usage policy and no traffic management is applied to this service.

Somewhat less than the £50.00 you were hoping to spend though!

Of this p2p, how much could you bear to do overnight? I ask this with plusnet/adsl24/aquiss/xilo/vivaciti etc in mind; they all have daytime limits but have unlimited overnight.

To be honest i can do 90% of this at night without it bothering me. I am currently with 1 of the companys you mentioned however due to a few long outages im looking at changing.

Have you found the reason for the outages? If not, the problem may go with you.

The outages are as far as I understand either network or exchange based as the problem would be that I was getting a sync just no connection each time I swapped routers and tried 3 different dns servers along with the routine of the test socket and no joy. This is why I am considering a change,

I did have previous gripes with the 21cn dlm putting me on a 3db margin and the connection be a bit flaky but I believe now the profile change time is almost instant, am I correct?

IP Profile changes on "BT" ADSL2+ (WBC/WBMC) are immediate, but SNRM is a different thing alogether.