Originally Posted by Greg in France

Gareth
I am in full agreement with Doug on driving it.
Having done that expansion tank hose test, I suggest:
Ensure the radiator purge system is unblocked by blowing through all pipes and tubes. Be SURE the thermostats have the bleed holes upwards, are opening in hot water, and all purge tubes are connected properly; post photos if not sure. Refill all (sequence: both caps off, radiator bleed plug out, header tank full to brim filling it slowly; cap on header, fill central spout SLOWLY until bleed plug running bubble free, bleed plug on, fill spout until full). Have car pointing uphill if possible.
Put the heater on defrost, start car, loosen bleed plug and continuously top up, spilling plenty no doubt but do not worry. Replace bleed plug.
Heater still on defrost take car for 10 mile run. let it completely cool and do not open anything. Then before opening any caps undo bleed plug and top up if needed. Replace bleed plug, remove expansion tank cap and top up tank, replace and do spout top up. repeat 10 mile run and let cool as before.
Then repeat the top up sequence and report back.
If loads of coolant loss on second go, pressurise system cold and see what happens.