Losing coolant

Hi, is the engine over heating and/or down on power? if so it could be a blown head gasket. Check for signs of oil in the coolant and visa versa. Any idea where the coolant is leaking from?

dont know where coolant is going just that the heaters dont work when it goes. no real loss of power just juddering on idle and moving off

If the heater is only blowing cold air, there could be an air lock in the system, but that wouldn`t explain the coolant loss. I would still guess at the head gasket or possibly broken water pump.
The juddering may be a seperate issue. Clutch?

had a new clutch fitted a couple of month back. i thought water pump after i fitted thermostat but wasnt sure. its only done 61k aswell

you could take the drive belt off that runs the water pump and turn it by hand to see how it feels when you turn it. If the heater has only been blowing cold since you did the thermastat, then definatly an air lock in the system- try draining and refill--very slowly and make sure the heater is set to the HOT position before refilling.
Not sure about the juddering. If it has got worse since having a new clutch, it could be a problem with the new one-just guessing tho.

heaters went cold first then it started juddering so checked it and found no water and the temp gauge was getting high. changed stat, still same but not getting as hot and the top hose going from rad to stat swells up

its probabaly the head gasket.