I'd avoid the PA role for the moment, it is just too murky and the course could very well end up being a very expensive mistake the way things are looking.
Is Graduate Entry Medicine (GEM) an option? If not, I think I'd go straight into work as a registered BMS, more secure, the jobs are out there (clinically and in industry) and there is progression. If GEM isn't an option and you wanted to do a masters, I'd recommend specialising your BMS, increasing your knowledge and earning potential. Or if you're looking for a change of direction and healthcare outside of bench science is for you, I'd look at a pre-reg MSc programme with an established, autonomous, regulated profession at the end (most of the allied health professions). The downside with those is that you would be graduating as a Band 5, same as a newly-qualifed NHS BMS, so financially it would be a disadvantage. It may just be prudent to follow your BMS route and specialise, unless you are really unhappy and there isn't a specialist route that would improve things.