"Dave Plowman" wrote in message ...

What's the best make?

Danfoss, IMHO.

And possibly one that can be repaired when it starts leaking?

Have never known them leak. Have known them stick shut, over summer in a
badly sludged system, but they are easily unstuck without the need to drain
down and with no more than a few cc of water spilt.

That will be 2d please.
--
Andy