Is there any chance to get funding through companies (environmental consultancies/big petroleum companies such as Shell, BP etc)? Have you checked whether BGS (British Geological Survey) has some PhD positions going? I think key will be that you find a university with a department/supervisor that covers your interests and that also has a good track record in getting funding for their international students (e.g through company funds, or through research grant money). No doubt, it's hard and these studentships/funds are scarce, but as was said before "dont give up". Keep checking all possible avenues. Also, if you want to improve on your applications, ask for feedback from the unis that rejected you. Sometimes that can be helpful...Good luck.