.... is on the cards tomorrow (it's being replaced with a combi system),
and never having done taken a cylinder out before, I would be grateful
for some pointers.

The space on three out of four sides of the cylinder is very limited
(it's in an alcove) but as far as I can ascertain, three of the five
22mm pipes which come down from the ceiling and go behind the cylinder
are capped off behind there (ie, redundant pipes from a previous
installation) and of the other two, one enters the cylinder at the base,
the other leaves at the top. I'll have another root around tomorrow in
the daylight, but does that sound a plausible scenario? There's no
boiler or CH, and HW is via an electric immersion heater only. There's
a CW storage tank in the roofspace. No valves or taps around the
cylinder (haven't checked up by the CW tank yet).

If I turn off at the mains, and run H & C taps until they run dry,
should I then be able to safely undo the fitting at the top of the tank?
If so, presumably the tank will then be full of water - do I siphon
that out? And then I can disconnect the bottom pipe connection to the
cylinder and cap that off?

Please let me know if there's a glaring error here or I'm going to get
very wet and/or do myself an injury tomorrow...!

Cheers
David