Thanks for all the replies, I didn't pay for the seat selection (free with a baby / silver card anyway). They handed out forms on the plane which my wife and I both completed (I noted all 4 BAEC numbers on mine), will also fill out the online form when I get home on Thursday.
just hope the flight tomorrow isn't as bad, it is already 40 mins delayed and I haven't even checked in yet. Oh - I couldn't actually get seats together on this flight anyway as the whole of row 16 (behind the bassinet) is pre booked, and with the 2-3-2 configuration of row 15, with 4 bassinets, I couldn't book 4 across and someone had already booked the seats behind the bassinet in row 26!
We usually fly Virgin as a family and they are a lot more family friendly.