TD5 Limp Mode

Hi. can anyone help? A couple of weeks ago, I lost all accellaration and my TD5 ground to a halt (but still idling). I noticed the temperature guage had shot right up into the red, but under the bonnet there was no real heat or smell. I re-started the engine, and the car ran fine - temp guage normal. A couple of weeks ago, it did it again ..... and started afetr a few minutes as normal. Today its done it every few miles all the way home. It will have to go into the garage tomorrow, but can you help me to know what the problem is (and maybe how expensive).

This is usually the engine loom wearing through and shorting on the back of the A/C compressor or dropping onto the hot EGR pipe.If the 5v supply wire to the ambient air temp sensor gets shorted it kills the 5v supply to the throttle pot.When this happens the engine ECU will cut the engine back to idle and ignore the throttle pedal - even if the supply is restored until it is shut down and rebooted.
Have a close look around the loom where it touches anything at the front of the engine,often its where the loom has been removed or replaced and not put back in exactly the same route.Re-taping the loom and repairing the shrouding is fine,but the last one I did had worn more than 1/2 way through the wires so it was replaced and routed correctly.

A long shot, have you checked the coolant level?