3 big heating issues!

So, when timer is off, the boiler is off when the stat is turned down and comes on (at some temperature) when stat turned up?

Do you have a multi-meter; and know how to use it safely?

 

I would say pump bearings have gone so needs new pump and valve also. Likely to be completely unrelated to any other failure of parts. Just had its life and is now ready for the scrap yard!

I would start by changing the valve head only, even if you buy it as a full unit - the mechanics are probably ok, its the silver head and that just comes off with a couple of screws.

You should be able to see if the mechanical bit of the valve is ok by moving the piece that is exposes gently and the ball in the valve will swing either way. Just done a two way valve that way at my place.
If you find it works but is still noisy pump, you can at least change both parts together and do the wet jobs in one hit.

 

I am not convinced that the valve is faulty. It doesn't explain this:

The heating managed to turn it's self on when the time is set to "off" and when the timer is set to "timed" and time is outside of the heating times. (I think?) But only if the thermostat is left on a temp where usually it would come on if the timer is within the heating times or set to "on" constantly. (post #19)

The fact that the thermostat still "work"s implies that it is obtaining voltage from somewhere. The question is: where?

This question should have been asked at the start: Is this (boiler running when it shouldn't) a new problem, i.e It didn't happen last year?

 

I asked Brez to carry out some basic tests on the timer to begin with, tho' there were chust things that came to mind and not 'proper' tests! But, if it looks as tho' the timer is working reliably, then we can at least look elsewhere.

A thought, Mr Spade - if the CH timer side is orf but then the DHW side switches on, if the valves is faulty (eg sticky) then perhaps it's letting CH 'let by' when it shouldn't?

So, the pump and boiler is running when Brez thinks it shouldn't be on CH, but it's because the DHW side has made it do so.

But, it's weird right enough.

 

We will have to wait for the OP's input (last seen post #19).

 

I agree this sounds like a 3 way valve not behaving as it should, and yes, I'd try just exchanging the head of the valve and not the valve itself. I had a problem on our old system, before it was replaced where the hot water would never come on if the heating was timed to come on from "all-off" first, so we had to set the timers so water always preceded heating, then everything was good. If it got out of step, had to turn everything off to reset valve and start again. Never did cure it - just lived with it.