mike ring wrote in
52.50:

Thanks to all contributors - I never managed to unscrew it, but got the H/W
pipe off and siphoned it out through the hole.

When I got the tank out I found the drain cock had the squarw bit buried
about halfway int the body, and the bit left poking out well rounded, so I
was never in with much of a chance.

Bit of easy C/H pipework improving to do, then more queries as I put the
new cylinder in....

mike