Thanks everyone who took the time to share their knowledge. I managed
to get the old olive off with the hacksaw groove/screwdriver twist
technique. I sussed out how the compression joints worked and I almost
had the first valve fitted! Unfortunately the tail is too long by about
5mill! I'm having trouble fitting the valves, even if everything was
tightened the bottom pipe is too far from the valve to slot in. Is
there a way to do this without removing the rads from the walls and
bending the pipe somehow? Heres a pic showing the closest the connector
can get to the pipe. There's less than 3 inches of copper pipe to work
with from the join below (that feeds to the rad on the other side of
the wall).

http://i29.photobucket.com/albums/c2...ung/TRV009.jpg

Could it be I should have been sold this model instead? It looks more
like the ones I had fitted and took into PlumBase to show them.

http://i29.photobucket.com/albums/c2...11_15mm1-2.jpg

I can get hold of an angle-grinder to trim the tails but I'm brobably
better served getting fully compatable fittings. Looking around there
seem to be several models that might fit the bill. I was sold the
Mistral M10, but I think it should have been the M11 (picture linked
above). Unfortunately Plumbase where I purchased the M10's does not
appear to stock them.