Boiler Tripping Out- Help.

[Drumnut]

I have a Main 24HE Boiler. It recently began tripping out (red light showing on control panel) Once reset it would fire up again. This began happening after we had a new wireless thermostat put in for the house and also sludge remover added to our hot water system. The heating engineer who did the work has replaced our water pump and valves by the hot water cylinder and also the temp sensor in the boiler in an attempt to cure it but the problem has got worse and worse. The boiler is now only firing after 3 or 4 resets and the cuts out after about 10 minutes. The engineer has told us that it is likely the spark generator and/or PCB but that the parts are obsolete so we should really look at a new boiler. But I have read that sediment can possibly block a valve in the boiler and cause firing issues?
My question is: Does this sound like the spark generator is the problem? Or should I be looking at a new boiler as my one is now obsolete? Or, is there anything else I can try? Obviously the difference between a £5 spark generator and £2K for a new boiler is significant.
If the problem does sound like the spark generator or PCB can I interchange parts from another boiler? The part numbers for my boiler are: Spark Generator: 5111922 PCB: 5110550.
Any help or suggestions much appreciated.