Thanks Dave. Unfortunately the directional TVR's were not fitted
correctly and caused prolonged banging. The Bar-Gauge on the boiler
itself would go crazy as the needle flipped.
I will be installing a room stat asap. The new TVR's are a necessary
measure right now to get Heatline to send an engineer again.
Heatline say that they will not send out an engineer until the
installation fault is made good. I've been unable to contact the
original installer, and his Corgi number is now registered elsewhere in
the country.
If you copy/paste the following urls and replace hxxp with http you
will see pictures of my problem at my photobucket account. I believe
this is within the rules as I am not including any HTML in my post.

hxxp://i29.photobucket.com/albums/c283/neil_jung/NEWTRV.jpg
hxxp://i29.photobucket.com/albums/c283/neil_jung/NEWTRVEXPLODEDVIEW.jpg
hxxp://i29.photobucket.com/albums/c283/neil_jung/OLDTRV.jpg
hxxp://i29.photobucket.com/albums/c283/neil_jung/StuckFittingOnPipe.jpg