Thanks guys,
Quite honestly the headset I have I bought from the flying school. It's unbranded, basic and cost less than £200 if memory serves - I think a new one is justified!
Looking around, I was struck by the affordability of the Sennheiser S1 Passive for its features. Reviews are rather good, but then they're generally reviews by proper review websites that will hardly paint things in a bad light. Any opinions?