Water running hot and cold

Earlier this year we had our boiler moved a small distance to make way for new kitchen cupboards. Since then (we didn't notice it before but we'd not been in the house long so maybe it was pre-existing) the hot water has been running hot and cold. We recently had both the bathroom and kitchen refitted, including the new radiators, and the problem went away for a while but is now back and getting worse.

When you run the hot water the boiler switches on and heats until it registers the water temp at about 90c then shuts off and the temperature rapidly drops to about 60c before the boiler kicks back in and heats it again, and so on.

It's a combi boiler, about 10 years old.

Any ideas what's happening?

I've attached a couple of pictures of the boiler in case they're helpful.