OK, I took the controller apart on my boiler and took some high resolution pics as below...
The numbers on the outer casing

The rear of the PCB

Closeup of the mains filter capacitor, you will notice that there are some components under it, rectifier diodes and resistors.

the main relay contacts

Mains filter cap from above

The remaining components - a few more caps, some diodes, two transistors and lots of resistors

and finally the whole device from above

It is all real basic stuff electronics wise, all the components should be available and easy to replace.
The transistors do have writing on the can but I was unable to read it with them in situ, you would have to replace one to read what they are.