Thanks for all the replies. I bought one from maplins for £30. Its about the same size as the piccy from smithy above.
Their ref no is L26BK. It's a single channel with one big remote and nice big button on it. It works up to about 20m away without an aerial which is fine for my jobs. Not much info with it and a link needing moving inside from momentary switching to latching but the wiring is simple apart from that. I will take photos and ask my 12 year old to put them on here
. I intend to fit one on my spare trolley so will try and take step by step wiring piccys. Someone bump this up if I forget.
Andy