John wrote:
Just as a side issue, can these low energy CF lamps be used in twin
concealed light fitting? The type that have the fitting screwed to the
ceilng and a glass dome covering the lamps.

If they physically fit, yes.
There may be an issue with them having slightly poorer life, if the
fitting is very insulating.
Of course, the fitting will run cooler than with ordinary bulbs, but the
CF lamps may be hotter than in free air.