2000 Vauxhall Corsa car cuts out while driving and will not restart, for several minutes.

Hi all,
I have a Corsa B (X reg 1.2 16v), which has developed a fault and I was hoping someone could offer a solution. About 7 months ago I got the ‘engine management light’ coming on while idling and I put it on the computer and it said the fault was with the ‘idle speed controller’(ISC), so I purchased a second-hand unit and it worked fine.
Anyway it has since developed a strange fault. It started with the car stalling at junctions and the engine would start, but would turn-over. So I popped the hood and checked the cables and it started fine. However it has started occurring more and more often even when driving along. I put it back on the diagnostic computer and was told that it only stated that the car had stalled and could not spark, the guy at the garage said that the ‘could not spark bit’ was because it had stalled.
After some investigation I have discovered that the car has to be left for approx 2 minutes after stalling before it will restart and that if I disconnect the temperature gauge and the reconnect it, the idle speed controller motor makes a noise and it will start-up fine. The only other fault present is that as with when the ‘ISC’ was playing up, the in-car temperature gauge has become faulty (the temp gauge on the dash next to the clock displays strange temps e.g. -60). I tried cleaning and then replacing the old ISC, but I still got the old fault and the new cutting-out fault. I have also replaced the plugs and checked the leads (you can actually see the cam turn the car turn-over when you try and start it, and the battery is new).
I would greatly appreciate any suggestions you can give to fix this. The garage says the only way to fix it is for it to stall and then keep replacing bits until it works again (a costly job) and the auto-electronics guy says it could be a few things, but he wants £40 an hour to look into it.

Please help