Thanks to everyone who has replied, some really useful info. I will try to answer all the points you've raised...
Firstly, this is not a building but a fairly recent refurb (office to residential c2016 i think?)
Not phoned anyone yet, am i more likely to get more accurate info through BT than other providers? Will i be able to switch to a better service without penalty if a better service is actually available?
Only uSwitch show anything, postcode not recognised as i mentioned before, but i also find it odd that not all the other ADSL providers are listed - I assume they are available if BT ADSL is. But i think i am only interested in BT/Sky and possibly Plusnet who I think are the cheapest from my searches so far.
The WiFI AP's i can see are probably in building due to distances to other buildings across a car park, which do not appear to be residentaial and strong signals. Probably neighbours using Sky so they get TV also as rooms are cabled with dual Sat points in multiple rooms (which i'm assuming is the use of the fibre box). But i cant afford and dont want sat TV, DVB-T is perfect for me. I'm only interested in fastest broadband.
@kitcat - Thanks for the DSLChecker link. Here are my results based on Post Code/Address: https://ibb.co/X7RK2GK
Is there a way i can check/test line or establish my phone number? I dont have a 'normal' wired phone, i could take one down to croydon, but thats more stuff to carry on train/tube. I'll not be driving down again until January. Is there a number i can ring from a line that has not billing/outgoing calls setup to determine the line number? This might help me get more accurate results in searching for a provider.
Thanks again, you lot are extremely knowledgeable!