Glow Worm 30ci - got hot water but no C.heating?

Firstly just like to say thanks to all that help on here.
I am fairly competent with this kind of stuff, and got a call today from my sister and brand new nephew ...complaining of no hot water and no heating.

Its a Glow Worm 30 ci

After a little bit of searching I read that the flexi-hose which connects to the expansion tank gets sludged up and blocked.

After attempting to drain the boiler, I realised it was indeed clogged. I removed the flexi-hose *Splash* and it was properly clogged. the expansion vessel emptied into a bucket and i cleaned out the flexi hose.

Put it all back together, opeoened the vent bleed on the pump....and built up the pressure to 1 bar....and run the hot water taps...to free the airlocks. Hot water then came ramping through.

I then went to test the central heating, and clicked the room stat on. The boiler went into a heating cycle and the rads did not warm up.

I opened the rad bleed valves but there was only cold water coming through.

Sister said that last night the central heating was working ok, if a little slow.

My mind now points towards the three way diverter valve, but I don't know if there is a way to test/check it before tearing it down?

I've checked and rechecked all the electrical contacts and connections.

Any ideas what to do here....or if i've missed something? Any help greatly appreciated!

Merry Christmas Everyone!
Tiny