Ok major cock up on my part, I have installed a 3/4", pre finished oak t&g floor over my old floor boards, which sit over a crawl space which is well vented by air bricks and not what id consider to be very damp.
Anyway the floor way layed last december, yes in a rush for xmas and not done as well as it could have been to say the least....
I face screwed round the edges and only blind nailed every 7 rows, as you can imagine the floor is raising in places, spongy and starting to twist in places.
I have accepted this needs to be re-laid and nailed every row, I was going to also put a sub floor down of 1/4 exterior ply to ensure level along with a vapour barrier between the existing floor and ply.
Would is also be advisable to place building paper on top of the ply?
Does all this sound the correct way of installing?
Also wont it be a problem if the nails puncture the vapour barrier and building paper?
Finally can anyone advise what most likely caused the problem, my poor instalation or maybe moisture?

I suggest starting by carefully reading the installation instructions from NOFMA. And if you only nailed every 7th row , that's a MAJOR part of your problem.

http://www.nofma.org/Portals/0/Publicat ... Floors.pdf

Thanks for that, what about the nails punturing the vapour barrier?

It is NOT a vapor barrier. It is called a vapor RETARDER. BIG difference. If you have a crawl space, the NOFMA instructions call for a 6 mil polyethylene moisture retarder installed on the earth under the entire house. It's all in the instructions. Read pg.4 , "Installation over wood joist construction."