Im sorry to sound rude but do you have any idea about aviation and headsets? Your option of a mach 1
Mach-1 Is totally inappropriate for a helicopter. You need to choose a headset with a fully enclosed ear on both sides, and prefferrably WITH ANR (Active Noise Reduction).
I am assuming its for a BIH pilot in penzance/Falklands, and as such you need to check their impedance as there is two types (low/High). I am fairly sure it's low impedance like our S61's.
I can highly recomend the Lightspeed Zulu as I use it now and have flown the S61 previously for 5 years and I would have loved to have used it then.
Si
P.S. I wish I had friends as generous as you.