disco td5 gurgling

been to Belgium and back from Cheshire no problems,last weekend went to north wales with a caravan on the back,started gurgling from the heater matrix and used about half a litre of coolent,pushed the engine hard on the way back and didn't use any coolent,just been having a mooch under the bonnet,silly question got a reasonable flow of water into the fuel cooler from the heater and a trickle out on revs,but a better flow on tickover is this normal.Thanks in advance for any useful comments lol.

Useful comments, not with out carring out tests, but air in the heater matrix and loosing coolent is a symptom of a iffy head gasket.

system sounds to be half empty

rad gets warm all over,expansion bottle at correct level,all pipes are warm/hot and are not to firm like they used to be before doing head gasket couple of months ago.After changing expansion bottle all problems went away until last weekend.