oxbridge mind for medicine?

Hi,
I'm thinking about applying to Oxbridge for medicine and saw that some companies offer help (e.g., Oxbridge mind).
How reliable are these companies, and is it worth using them (as they are quite expensive)? Do they actually provide any useful help/tips/advice?

Please don't spend massive amounts of money for these things, they help of course but all they offer can be done yourself.
The only things I'd recommend buying is medify/medentry for the ucat when the time comes (2ish months before your date) and maybe some interview practise but you can practise just fine with friends, parents etc.
Free resources can be found everywhere, the ucat website has lots of materials, and sometimes universities hold days where you can practise interviews or write your personal statement, all for no money.
Best of luck!