strange overheating issue ?

[sjr-997]

Hi, its a sunny day and my birthday so time to get the R300 out ! I last drove it last weekend, and all was well. This morning I get about 3 miles down the road and I notice the water temp gauge is getting progressively higher, past the 90 degree mark (normal, needle vertical) so getting a bit chilly i turned the heater on. needle kept climbing...i backed off...needle still climbing...got to a safe place to stop and by now its nearly hitting red...stop the car and take off the engine cover...car isn't very warm, in fact I've had it a lot warmer when out for a blast...so.....scratching my head. the fan hadn't come on. the water pipes were relatively cool. cool enough to touch...so I don't 'think' its really overheating. I checked all of the eletrical connections to the fan and thermostat...they are all on tight...so I sat and waited for 15 mins to let it cool. turned on the ignition and engine and let it idle and it had by now fallen to 90 degrees. i let it idle for 2-3 mins and it stayed at just over 90...normal standing temp...so I had to get it at least home...so drove it carefully for a mile....temp had now fallen to straight up 90...normal, kept going for another mile at about 40-50...its fine..., now it seems fine...obviously I'm concerned, but where do i start to troubleshoot it ? the car has only done 2000 miles so is like new. the water is fine in the expansion tank and the hoses aren't damaged (well a bit brittle) but not unusual. oil pressure is normal, car idles fine, and drives fine. strange ? looks at first glance elecrical related...reminds me of years ago a mini i had with a faulty temp gauge...but only discovered it after replacing the sender, thermostat, some wiring and then finally the gauage !

cheers, simon