On Wed, 28 May 2008 21:48:56 +0100, A.Lee wrote:

First thought, air in system, though bleeding all the rads doesnt
produce much air - typical of what I'd expect after not being done for 6
months.

Shouldn't produce any "air" at all after a system has been in use for a
while. Routine bleeding of radiators is indicative of either lack of a
inhibitor (thus the "air" is hydrogen from corrosion of the steel rads) or
there is fresh water being introduced on a regular basis.

Pressure now down to 2 bar when it is cool.

Pressure gauge was lying initially, did you give it a little tap?

--
Cheers
Dave.