Bulb has gone but cover removal needs a triangular key – any idea where I could get one and are they all one size ??
Local (small-ish) B&Q didn`t have a clue ….

Get a bit of soft Pine wood, a chunk off a pallet is fine.

Get a sharp knife and carve the end of the wood into a triangular shape that fits.

It takes a few seconds but I’ve never found an official tool and this approach always work and costs almost nothing.

Correctly sized screw driver will do job as well

If it’s like the triangular thingy on my outside gas meter, which is about ten mm corner to flat, there’s a tool I have. It does radiator vents and stop-taps too. This looks similar…

http://www.screwfix.com/p/plumbing-tools-by-rothenberger-4-way-radiator-services-cabinet-key/84379

As above, you must have a flat screwdriver/allen key that will fit? Only other suggestion is one of those four head radiator bleed tools (shaped like an X) I got one of those in B&Q…sure one or two of the ends is triangular

(Oh yes, just like the post above from 10 minutes ago!)