Just got an email to remind me that I'm not going to receive anymore paper bills .

They claim I already know about this from a recent email they sent me I've just checked all emails for the last 4 months and no mention of it anywhere.

contact BT Support - they regularly check in on this forum.
will be able to put your mind at ease and check things for you.

IMO - check your BT.com account and consider changing the passwords for peace of mind.

Could well be that you signed up months ago to paperless billing and they are just getting round to changing it or they didn't send you confirmation at the time. I have 2 or 3 BT services that I set to have "paperless" billing however I still get a regular statement for BT Mobile despite it being one of those "paperless" accounts... (hope that makes sense).

No I would know if I'd signed up This is how they put it

BT do tell lies
They wrote to me in August last year saying that (as I had asked) all my calls would move to BT on 7th September 2009. But they didn't actually move them - which I only realised when my old provider tiscali/talktalk sent me a letter threatening a debt collection agency if I didn't pay them, and stopped me making phone calls.
I haven't actually had any bills from tiscali/talktalk, but the helpful man in BT complaints said it was my responsibility to check whether BT were billing me for calls. Which they weren't but then I'm on a free evening and weekend package anyway....