CH timer replacement?

[GaryinAshby]

My parents elderly CH timer has packed up. Its the older "clockwork" type. You can still switch the heating/water on manually, but the clock has stopped working. Is it straightforward to replace it with a new digital type? There are three cables feeding into the existing timer, I'm guessing one is power & one for CH & one for water?

Thanks

 

[namsag]

Is there any model name on it , As you maybe able to get a digital onto existing back plate without altering any wiring