Light piston refurbishment

[sarboy w****r]

Hi there,

Does anyone here know after how many hours an aircraft piston engine will need to be refurbished (UK) please? Also, how much would it cost to have done (very rough figures ok)?
Finally, when buying a secondhand aircraft, I gather it's a good idea to get an aircraft survey done - can anyone recommend one and tell me how much to expect to pay?

Thanks,

SBW