It could be your engine fan kicking in... possibly.
I have a 2000 Escort Estate with the Endura Turbo Diesel engine, and that does feel a bit rough when the fan kicks in. As for your temp gauge, mine sometimes goes off on one every now and again, especially when it's on it's way to the 3 quarter mark. The fuel gauge isn't anything to shout about either
Next time it does it, pull over and check to see if the fan is on