The 73 rating is a bit of a dead rating in Europe to be honest with you, unless you want FR. When I look out of my 737 window, I mostly see Airbus 319/320 here in Europe. Certainly if you want to fly the 737 in the UK, there's not much choice of airlines to go to, even less if you are 300-500 rated.
The 757 rating is very overpriced, Bond charge GBP27K! I don't know of any other establishment with a 757 JAA rating which offers non-airline bods a go, as I think GECAT and Alteon don't accept private applications.