In article ,
Christian McArdle wrote:
Heads often don't cost much less than the complete valve, so you
might consider buying the whole thing, so that if it turns out
that the valve itself is knackered, you've already bought the bit
and can reunite the new head and valve.

IME it's easier to replace the Synchron motor (£10+VAT or so),
especially if the lead on the existing head disappears into a rats
nest of wires.

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk
Free SEDBUK boiler database browser http://www.sda.co.uk/qsedbuk.htm