I've had fun tonight. Decided to grease and check the wheel bearings. All OK and good.
The retrofitted a temp gauge. I really like my old dash with the griffin instead of the temp gauge, so I got another dash and took out the temp gauge and fitted it to my old dash. Good old Vauxhall - the wiring was already there and in fact it looks like the wire to the temp sensor is actually cut near to the coil wire and then sealed off. Funny to think they'd do that, but I suppose it stops there being a loose wire dangling. Just added a new bit to it and bingo.
Works well and looks good - but more to the point, it stops me driving with the heater on to check it hasn't run out of water and overheated!
The fruits of my labour