Energy finance career paths

So I'm a UK student just about to finish lower sixth(penultimate year of high school) and will be applying for universities in October-January.
Providing I get an offer, I'm hoping to study Earth Sciences at Oxford, although Imperial, Durham and UCL would be my back ups. However, rather than going down the research trap that Oxbridge seems set up to do(as opposed to many of the top American unis), I'd like to enter a commercial role afterwards, probably with an eventual view for energy equity or trading, particularly with a focus on Cleantech and renewables. Particular areas of interest would include solar and geothermal, as well as the increasing demand for lithium as the developed world begins to switch to electric vehicles.
Now in terms of the career path, what would people here advise? If oil is booming again in five years time then that may be an option(although I have conflicting opinions on the ethics of certain geographical localities of the worldwide petroleum business) and it may be worth taking the extra year at Oxford to get an MSci straight away, but in terms of switching over to the finance side would a Masters from Imperial in Metal and Energy Finance be enough? Other options would be Geneva, Aberdeen and Cass by the looks of it. Would having my undergraduate degree in the physical sciences be detrimental in the long run, or will it help to have the scientific and mat magical background in terms of trading? Would it even be worth entering the physical side of the energy industry for a few years to gain more experience?
I'd be quite happy to travel and work long hours for a couple of years, but ultimately I don't want a job of the same hours as investment banking so a work-life balance would be a priority. I've read some threads here and there appears to be a few engineers that have done the switch to finance but not that many theoretical scientists, so any and all advice is much appreciated.