Looks like it's sorted. I used a nut and bolt to anchor the spring and it seems to be OK now. My fiddling with the switch on top doesn't seem to have had an effect, though I'm still not sure what position it should be in - but I'm leaving well alone!
Thanks for your advice, it was invaluable...
Thanks for your quick response seco.
So have I messed things up by fiddling with the manual override switch on top? It did seem to turn the rads off when I moved it. Any idea what its default position should be, and whether it'll just flick back to it automatically (fingers crossed)?
No...
I have a problem with my gas fired heating system that I hope someone can advise me on.
During this hot spell I've been wanting to turn the CH off in the evening while leaving the HW on. However simply advancing the 'heating' button on the programmer had no effect, nor did turning the heating...