You know in the UK its not a pre-requisite at all uni's to have an MSc first. The only way to find out is to write a strong CV/personal statement cover letter etc telling them about your commitment to what you want to do and that you have some research experience already. The only way to know for sure is to send it out there.

Also you can get funding for an MSc (I had a studentship for mine).

Hi, I currently work in Research in a Molecular Biology Lab in the US. I am a British Citizen and been here two years. You will need to take the GRE.