i have got one large radiator in the lounge with a trv fitted

Sounds like air, drain down refill and get the air out one rad at a time

The trv is on the wrong end. Older types of trv had to be on the flow pipe to the rad, if they were on the return they would 'hammer' as they got to the point of shutting down because the water would be pushing on the valve [that's why it stops when you adjust it]. Modern trvs can be fitted on either end and are termed as reverse flow or two way. Your easiest solution is to replace the trv for a modern one.

It's most likely caused by expansion of the coils in the radiator. I doubt the level of the radiator has anything to do with it. This can most likely be fixed by having a new radiator installed as the new one would tend to expand less. I've also used fin tube in place of radiators because they're much easier to maintain and are more reliable.

I admit that I live in an area where radiators are not that common so my experience is limited with them. But expansion is usually the cause of most banging noises associated with hot water.