Comms are sort of my thing, so I can probably help here a bit.
Radio wise; get a baofeng, don't f*ck about with anything else. Baofeng UV5-R is without doubt the best radio possible for the cost.
Headsets is where it gets more complex, if wearing a comtac/sordin type headset with a helmet you're going to want to put them on arc rail mounts (the headband is SO UNCOMFORTABLE). You'll also need to consider what headset you want, real comtac/sordin headsets with attached microphones are made for military users and the microphones will require an amplified PTT switch to work with a Baofeng radio. This will add on another £100 just for the PTT, add that on to the £200+ for the headset and £50 for the arc rail adapters and it becomes an expensive prospect.
On the other hand though replica headsets are normally quite fragile and provide absolutely NO hearing protection, I had a couple of them go tits up before biting the bullet and going for a real headset.
Most economical option is to have a comtac XP headset without a microphone (much cheaper than the Comtac 2/3 military headsets). Then get a baofeng radio with a fist mic that has an earpiece plug and use a cable to connect your headset to the fist mic. You'll then have comms wired directly into your ears in super clarity and have a microphone that definitely works with your radio. Only downside is not having the mic immediately in front of your mouth all the time.
Do it that way and you'll save probably £200 for a high quality real steel headset that provides solid hearing protection and extraordinary audio quality, along with a decent radio and compatible microphone.