Presume you will want to apply to queens, they’re also only 4K a year lol. It’s an undergrad medical course but you can do it as a graduate entry, around 1/3 or more of year are graduates, plus queens likes grads.
Only thing would be that business isn’t a science degree and therefore mightn’t be eligible for entry. You’d need to check up on the entry requirements though. You’ll need AAB at A level if you are ok with the business degree as it’s a 2.1
Will also need to sit ukcat and have work experience.
I think it’s great that you want to do medicine, however you are 43 - say you get into next years entry so starting 2019 - you’ll be 44. By the time you graduate you will be 49. Then you have 2 foundation years which are compulsory before starting speciality training. So that’s 51.
If you do GP it’s a further 3 years (the shortest!) so you won’t be a fully qualified GP until 54.
If you want to do a speciality then it’s 2 core training years after foundation as well, so you won’t actually be working in your speciality until 54, perhaps making consultant level when your 59/60.
By all means go for it, but just be aware that the hard work continues after medical school and you mightn’t want to spend your 40s/50s in meducation.