Strange G10 downlight fitting - stuck

[offgridAndy]

You can purchase for very few English pounds a adjustable pin "spanner" for removing the retaining plate on a disc cutter. Pins are about 2.5mm dia but could be ground down a bit if required.

 

[Morello]

Search on Google or eBay for Camera Lens Removal Maintenance Repair Spanner Wrench Opening Tool Kit.
They are adjustable pin spanners .

Thank you.

 

[Morello]

I don't know what the diameter of the fitting is but one of these opens up to about 60mm and may do the job

I'd like to thank you for this suggestion, there were various steps necessary including WD40, and each fitting had to be removed from the ceiling causing minor damage but ultimately this little tool is what made the difference. Using a screwdriver I was able to twist the notch on the bezel slightly bigger so the tool fit better in the notches and gave just enough purchase. LED now rules. Thanks again - but what a faff!!!