I'm having a little trouble with my temp gauge, which I'm pretty certain is due to a slightly dodgy connection at the sensor.  The connector is jammed on really tight and in a very awkward position.  Before I get tough with it though I thought I'd ask whether it is simply a straight push-on connection, or whether there is some secret to getting the damned things off!
 
Thanks, and Merry christmas to you all.

The temp sender connector is just a simple spade terminal.  It's usual issue is falling off, because it doesn't have a good locking tab.
 
We are talking about the same connector, aren't we?  Single wire spade, located on the inlet side of the motor and just below the top of the block line?

I thought the temp sensor was the green plug attached to what I gather is the thermostat housing at the rear of the block towards the bottom of the head.  It looks to have two terminals, (judging by its size) and has a rubber boot over part of the wiring, which disappears into the loom in short order.
 
I gather there is at least two water temp sensors; one for the engine and one for the radiator fan.  My gauge fluctuates occasionally, and I'm confident it isn't an air pocket in the cooling system because (amongst other reasons) sometimes I'll start the engine from cold and the temperature go straight to its warm reading.  At this stage I just want to eliminate corrosion on the terminals as a possible source of incorrect resistance readings, but to do that I have to (a) identify the correct connectors, and (b) get the darned things off!
 
Thanks.
 
 

Sensor for the gauge is just below the oil cap, its a spade connector;
 
Water outlet either has one or two sesnors, green and brown.

as mentioned, the two pin coolant temp sensor on the back of the head is green or brown. this is the temp input to the ecu. this sensor has a metal clip holding it on - it is the same as a Bosch injector connector. quite often if the plastic that holds the wire on breaks, people glue them in place. if you are having issues with the reading on the gauge, this is the single wire temp sender the others are mentioning. if this is playing up, check the wiring, and consider replacing the sensor. they can be bought from repo or Burton's for as little as $10.