Just bought one of these s/h. There was no relay included, what do I need and will I be able to get it from Halfords or similar? Any useful tips on fitting generally?

 

Use a heavy duty relay (at least 30 amp). If you are using the 130w bulbs this is a 22 amp constant load, more on startup, and this is too much for a normal one.

Take the power feed direct from the positive battery terminal and fit a 30 amp inline fuse.

Take the trigger wire from the main beam wire (yellow one on the headlamp bulb connector plug).

Use decent thickness cabling and make sure your earth connections are good.