Thanks for that. They are 4mm apart (centre of pin to center). The old and new bulbs both say 12V so I guess that means transformer
They have been installed when flat was built 10 years back. I know nothing about electrical fittings so I guess this is an electrician job then, would you agree.
By...
My pair bulbs started fluckering after 2+ years so I assumed the bulbs were at their life end. But replacement units still flucker.
I assume MR16 is the code for the fitting which are 2 pins about 1mm in diameter. They look like this...