"Kalico" wrote in message
...
Please can anyone tell me what they think the best board to use behind
the tiles of a shower?

Wedi board
http://www.wedi.co.uk/flash.htm
It's lighter and easier to cut and fix than Aquapanel. Might also be
cheaper.

Obviously, regular plasterboard is cheapest, but useless if it gets
wet. Can it be coated with PVA to help?

No.

Also, can the tiles be fixed straight to the board or is it essential
to plaster first?

Yes/No