Thanks again for the replies.
After chatting to a mate who's probably forgotten more about this sort of thing than I'll ever know I went for a Ubiquity outdoor AP.
https://smile.amazon.co.uk/gp/produc...?ie=UTF8&psc=1
Works very well, I just needed to route an ethernet cable from the router/PoE adapter in the living room through the garage to an external wall and round to the back of the house. Oh its a bugger to set up as the controller is through the internet, not direct to the unit itself.