I’m fortunate enough to have the Bupa’s through work. (It does my yoghurt-knitting reputation all kinds of harm).
Having hit 50 myself last year, I took them up on the offer of a full health check and I have to say, it was incredibly (and occasionally invasively) thorough.
If you have private healthcare, I’d get straight onto it. In fact, even if not, you can always pony up and pay to get a decent examination.