I phoned HYMS, they said they score your application :
30 points gcse, where an A* is 3.75, A is 3 and B is 2.25.
40 points ukcat, where each decile is 4 points
15 points SJT, where band 1 is 15, band 2 is 10, band 3 is 5.
Contextual is 15.
Cut off last year was 54.25 out of the 100 points