On 07/12/2016 17:34, ss wrote:
When I reposition my ceiling light fitting must I attach to a batten
spanning 2 joists or can I fix a batten to the topside of the
plasterboard ceiling.

I don't know the regulatory position, but if you slip while changing a
bulb you could do a lot more damage with the latter method.

Cheers
--
Clive