That valve is a honeywell 3 port on a y plan system, the little leaver on the bottom manually moves it over to heating you push it over then let it come back to hook in the little slot try that and if heating works the syncron motor is gone not so easy to change as its facing away from you but...
If you have a valve that the boiler feed goes to in the middle and a pipe out each side for hot water and heating then you a Y plan set up if its a honeywell valve with a silver metal top is the leaver at the end loose when heating is on if there is resistance against a spring then the syncron...
I have been informed by Alan his son that he passed away yesterday after a very short illness, he joined LZ september 2006 so has been on here a long time with lots of helpful input he will be missed
RIP Tony
You have an old style gravity hot water pump central heating system are you sure the pump is working correctly, just because it is turning dose not mean it is working with any omph.
Hows the fluid level it needs to be topped up with engine running as the brake booster will drop the level and the clutch out let is high up, never had issues how about an easybleed kit.
Its steep because they cut to much of the bottom rung, you alter the the top stays to limit the angle the hatch comes down then measure from the second section down to the floor and trim the bottom section to suit , i have fitted a few