The valve is opening and I did consider trying a poke through but with very little pipe to hold onto and lying flat on the floor while trying to manoeuvre two arms under kitchen cupboards I did not fancy trying to stem the flood when it came even though it is a pressurised system, plus I was worried that if I damaged the flexible pipe I really would have a major job on my hands. We have managed most of the winter without it working so until milder weather. I did try flushing under pressure from the filler hose, the pressure relief valve on the boiler does not kick in until it exceeds 3 bar but that did not do anything.

Richard