I think my 330/12 has an action is so low that it stifles a little when you hit it a bit harder.

I don't mean fretting out in the traditional sense, as it plays cleanly on every fret on every string. It's just when you give it some welly it sort of acoustically compresses.

Because of the nature of the guitar I don't really want mess about myself with the set up, so I thought I'd guage people's experiences.

I don't want to mess with the set up too much because I really like playing the guitar most of the time and the intonation is spot on - I assume that the guitar tech can manage it but was wondering if this was something others had experienced.

It sounds like you may need to raise the bridge a little. Also try adjusting pickup height.