There are plenty of people that do this and there is some good advice above.
It sounds like you've thought about the financial implications, but to reiterate: You'll need to be able to dedicate enough time to your pre-university qualifications, then go through 5 years of med school during which SFE will probably give you £3500pa to live on for two of them, then you will need to be paying them £9,000 for two (maybe 3) more. You will then be an FY1 on an average starting salary of around £26,000 (based on a look at the new contract), which may or may not be less than your current salary. It goes up relatively sharply after that, but you will be working a lot of weekends, evenings and nights for at least the next 5 years - I don't know if that will affect your home life at all.
Its a huge financial commitment basically!