Electricity st, next to Accy Asda, there is a leccy shop there.
They have them all.
You need to know what you want though.
Will be cheaper than B&Q etc, called Denmans I think.
Denmans Electrical Wholesalers Ltd - Suppliers to Commerce, Industry and Related Trades
Page 30 of the catalogue.
I have the anti corrosive fittings in the kitchen, single 58w ones.
Do the job for me.