Okay so ive changed the faulty TRV and locksheilds in both bedrooms. Also i have added a water hammer shock arrestor close to where the banging was coming from.
Now its a very small tapping noise, there is no movement in the pipes at all when i hear it so i dont think its movement in the pipes.
The pipe work to the rads contain approx 4 90 bends. Could this be cured by simplifying the pipework?
Also it sounds crazy but what if i wrap the pipes in question with insulation like this http://www.tundrafoam.com/tundra/tundracommercial.html as sound proofing to muffle the sound, you think that would work?
Any other ideas? Ive tried turning down the pump, and pressure in boiler is 1bar when cold.
Thanks