Xantia Heater Blowing Cold. Also Tick Over Problems.

[goddardo]

My 1999 Xantia Sensation's heater has just packed up which is a pain at this time of year.

The problem seems intermittent, in that it comes on warm for about 5-10 mins then goes cold again.

Also the Tick over seems to be going up & down. Sometimes it won't idle. It just stalls. Other times it can over rev.

Any info would be much appreciated asap before I push it into the nearest quarry :(