I've been looking at shower trays in B&Q and Wickes - the cheaper ones, &
its not apparent how they are fixed to the floor.

No obvious clips, lugs or anything I've spotted. Can't pry any instruction
leaflets loose from the packaging :-)

How exactly are they fixed down?

Second question. It makes sense to me to cover plasterboard with aquapanel,
fixing it so that the aquapanel overlaps the shower tray by its thickness,
then tiling over it, providing a much better waterproof joint.

Someone has remarked that the plasterboard should be 'replaced' by
aquapanel. That would leave a smaller overlap over the shower tray, not to
mention more work & mess.

Granted some thought about covering the edges would be required, but I can't
see the point in removing perfectly sound plasterboard.

BTW - when they install a shower in a new build, do you reckon they use
aquapanel or tile straight over plasterboard?


--
Dave - The Medway Handyman
www.medwayhandyman.co.uk