Electric engine fan query..

[tweak'e]

Many thanks, how do I make a pressure tester? I'm thinking I'd need to remove the thermostat, drill a hole in an old rad cap, fit some sort of pump etc?

a mechanic will have kits for this. a pressure cap adapter, pump and gauge.
after you fix the obvious leaks, leave the gauge on it over night to see if there is any pressure drop.

Remove the overflow pipe at expansion bottle.Use a bicycle pump with a small adapter eg cut out a valve from an inner tube. insert valve into pipe leading to radiator cap & pump a few times,only requires a few psi.

pressurizing should reveal leaks from hoses, rad etc.

nice !