looks like the 3 way valve has expired inside the valve itself, mine is a pretty old sunvic with 4 wires (blue,orange,red, grey), all the ones at screwfix are either 3 or 5 wire, timer is a satchwell.....am i heading for a world of pain ?
Sunvic are still available. Modern Sunvic equivalent would probably the least painful if not a bit dearer than screwfix.
yea but they are all 3 or 5 wires now, dont want it letting the magic smoke out
Assuming it's listed, this may help.
http://www.sunvic.co.uk/downloads/product-wiring-diagrams-help/
Is then get the writing diagram from what ever Screwfix sell and see if it matches.
(Although really I'd go to a plumbing merchant and say "I want one of these" and show them your current one)
In fact I think this page tells you how to map old valves to new wiring
http://www.sunvic.co.uk/downloads/product-wiring-diagrams-help/?resourceTypeID=12419
Thanks Mike, ill have a read