Slipping cranks, drive chain slip?

Every time there is one of these threads it turns out to be a cog slipping problem. Yours may be the exception, it's possible but unlikely. Take off lock ring and cog, check threads yourself.

Otherwise check chainrings bolts, crank bolts, feel for b.b play and roughness, feel for cone play on the hub check your track nuts are tight, all after you've check the hub threads,

Cheers for your help tommy,

will do once i get access to the tools!
Wasn't gonna start a new thread, but as you said all the other slipping threads appeared to be about loose lockrings/cogs