i have a circulation problem in cooling system ,i have flushed radiator out three times with rad flush what seems to be happening is when i go roun d the corner and the engine is warm the heater blows hot then after awhile it goes cold temp goes right up then drops back to normal then when i park up and start up next day i can drive allday and it still blows cold changed thermostat ,put new water pump on for some reason it does not seem to be circulating through the block only now and again bled system many times but still wont circulte proprely by passed matrix can anyone help its a 2.5 tdi disco dont know lost

Does your water pump run off of the timing belt or the fan belt?

fan belt

Is the belt routed the correct way?
Is it tight? A loose belt will slip and not turn the water pump fast enough to cool the engine.

It sounds to me like you still have air in the system.

Stick the nose of the truck up higher than the rest of it and try bleeding it that way.

What is the exact process you have been using for bleeding the coolant system?

i filled it up through radiator took the cap off squeasy hoses will check which way pullys are on ,bigger problem now cylinder head blowing oil out tapets come loose stripped head off to be reskimmed ,do i need to put new bolts in head ,to be honest think i bought a lemon lol

That is the wrong way to bleed any cooling system.
You must top it off, leaving the radiator cap off, start the engine and let it idle with the heater on full hot.
Keep the cooling system full.
Once the upper radiator hose is to hot to touch and you have good heat out of the heater replace the radiator cap.
Use the truck.
The next time it sits over night check the coolant level and top off is needed.

yes you will need new head bolts, you ALWAYS use new head bolts.