ok im keen 2 figure out the problem 2

The radiator is definately cleam and good as i got it all redone just before the engine went in!!

Yes the car does cool down when going down a hill idling, but only slightly

No it doesnt heat on short runs

Yes it does gradually heat up on a long stretch of road with the pedal on the floor

It sits under halfway when idling

No major bends in pipe

There is good circulation in the radiaotor, but i have not checked it at revs!!

Hope this is enough info.
Thanks 4 the help