Right - an update for any of your who are interested
Finally managed to get an Electrician round - seems as though there is a problem with the switch wiring whereby the live and earth are shorting out. The people in the flat upstairs had been doing some work, so maybe they put a nail through it or something - who knows.
Unfortunately due to how it's all been wired up, looks like it's a messy job to replace the wire, so the sparky has suggested a remote switch set-up as a quicker and cleaner option.
Didn't even know that such things were available and look quite cool, just a shame we're looking to sell up, otherwise would consider putting them in on a couple of lights.
Anyway - thanks to all of you for you advice and comments and hopefully will cross again in the future.
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