Stephen coughed up some electrons that declared:

On Thu, 20 Aug 2009 16:46:23 +0100, "Toby"
wrote:

Well, you don't need to drain the hot tank, just drain the cold,

That's true but how would you do this without making a mess? The only
way I can think of is by bailing out the tank with buckets or
siphoning it but that requires getting to the tank in the loft. The
problem is that no-one has been in the loft for years, there's no
lights up there and no boarding, so it's an expedition I would like to
avoid if possible! I'm still hoping there will be a valve in the
airing cupboard

Turn off the water main and open the taps until they stop running?...

OK you waste some hot water but it's easy.

Cheers

Tim