You would have to solder the two wires for each side to whatever type of connectors the fog bulbs need.
For the expansion tank socket you would need to chop it off and strip the wires, for this one i would use bullet connectors that you crimp on. Cheap from halfords again...
You would put a single wire, that you stripped from the socket, into one end of the bullet connector and the two foglamp wires (ie. both positive wires) into the other end and then crimp them. Then repeat for the other wire.
If you were to solder these wires it would be the 'Y' connection (ie.wrap two positives from fogs onto the one positive from socket and solder). Then wrap with electricians tape! I don't recommend this way but i have done worse in my time!
