Went I make this flight at 50000 ft from egll to kjfk, they start my descent from kbos to kjfk 50000. went I got kjfk I was still too high to land. Question is there anyway to start descent before.

I don't think so, but I believe the Concorde slows to sub-sonic speed either before or early into it's descent from flight level. This should put you at the correct approach altitude for JFK, but watch your fuel level, as this aircraft is much less efficient below Mach 1.Hope this helps,John M.