JBG wrote:
Replace the fuse in the dimmer switch if it has one, otherwise replace
the whole switch. (To test this hypothesis, remove the switch and
temporarily connect the two wires together with a choc-block terminal.
Turn the power back on and if the light comes on the trouble
definitely lies in the switch.)

http://nickmyers.co.uk/Wiring.gif

Nice diagram: cables 1 and 3 are the supply-in and loop-out to/from
the rest of the lighting circuit, 2 goes to the switch and 4 to a
bathroom fan. BTW the brown and blue on terminals A and H are the
wrong way round, although the neutral and live labels are correct.


Thanks Andy - the hypothesis test works (wish I hadn't bought a new lamp
now, but it's nice so might as well fit it!) so I'll have to buy a
replacement switch, the fuse must be sealed inside the plastic box on
the back of the switch...

Thanks for all your help guys - pays to ask the experts!

The clear picture really helps - wish I had a pound for every post here
which starts off "...so I disconnected the ceiling rose and now there's
all these different wires hanging down so how do I work out how to
reconnect them....