Pre-EASA, JAA counted 10% of my 3-axis microlight hours towards my JAR PPL. If I'd done it a couple of years earlier as a UK PPL, IIRC I'd have been allowed 35 hours off the 45hr minima for my UK PPL(A) for holding a UK PPL(D).
FAA counted all of my 3-axis microlight hours towards my FAA CPL.
In EASAland, EASA counted none of my microlight hours towards my EASA CPL.
The goalposts keep moving, but so far as I know the only one that really matters is that you can count 3-axis microlight hours towards SEP currency in EASAland right now. I've heard of proposals for microlight hours to count towards the EASA CPL, but nothing concrete - and with the UK now leaving EASA, that lobby is likely to be much weakened. Maybe in coming years they'll count in some way towards a UK CPL and more generously again towards a UK PPL, but I wouldn't hold your breath, given all of the other, and to them higher, priorities UK CAA will have to deal with in its first few years flying solo again.