On Sun, 15 May 2011 11:34:46 +0100, A.Lee wrote:

If the existing wiring is sound and the sensors, panel and sounder
are
in the right places its a simple swap out job.

No, complete rewire, so best done while doing that.

I think the statement "existing wiring" was refering only to the
alarm wiring not a what I think you are saying a complete mains
rewire.

The old one is unreliable, with numerous wires going all over that
cannot be traced, so I dont really want to work on it to try and fix it
when new alarms are £100ish.

A tone cable tracer will make working out what cables go where a
doddle. Hang the sender unit on the remote end and then see which one
it is at the panel, label, move sender to another cable end repeat. A
new panel and sensors would be far more reliable than wireless IMHO
but then I don't trust wireless for "critical" applications without a
hot spare backup...

Not sure I trust something that could be jammed with a lowish power
RF noise generator.

--
Cheers
Dave.