Well before I saw your reply I've now bought Unibond flexible wood and concrete floor adhesive/grout (more expensive than Wickes and B&Q own brands) and it says clearly on the instructions on that tub to use Unibond PVA to bond the plywood surface, so I've got some of that too.
Everything I've read says use 'dry to touch' PVA between the adhesive and tiles so I've bought Unibond's recommended, which is of course their own and that tub also says it is suitable to bond porous surfaces like plywood sub-base etc.
is this a spammer???...
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