On advice checked all switches on affected area of lighting and bulb holders and tried to tighten any screws. Also cleaned out dust and cobwebs from ceiling roses. The lights all came on but then went out. Bulbs are working. Energy company suggested a problem in the fuse box. It has been fine until a smart meter was fitted a few weeks ago. Don't know whether fuse box had to be touched? I assume not. Other lighting in the house fine. Found one loose wire in a light switch and re-fixed that and lights came on then went out again.
At a bit of a loss now