The older ninja 250r (not sure of the name in the UK) probably fits a little better than the newer model of the 500r. Both of those have fairing cutouts that interfere with the knees on long legged individuals. The Suzuki GS500F also seemed to fit better.
I think supermotos are a great way to go for a first bike, especially for taller individuals. They are very light and have taller seat to peg distances. Plus they look quite sporty (atleast to me).
I’m 6’2″ and ended up with an `06 Ninja 250r, mostly due to cost. The ninja was like new and less than half the price of any used supermoto I could find. Plus its a great bike. Just could use a little more leg room
And definitely look into bike restrictions in the UK. I’m not sure you can buy a 500cc your first year.