I would do the foundation degree because QMUL is a nice uni with great facilities in Central London. I would hate to be in the middle of Hertfordshire or in Uxbridge, and the uni's location makes a big difference to me, so yeah I would do the foundation.
If you don't care about any of that though and you just want to go to any uni, I wouldn't bother with the foundation, unless you particularly like QMUL over the other two. But in terms of jobs you can still apply to graduate entry medicine, or work in medical research with a Brunel degree.