COA flies 752s from EWR (Newark) to both GLA and BHX (Birmingham) daily or more. They do this themselves in a US registered aircraft - as well as within agreements with British Airways and BMI to name two.
Northwest has agreements with KLM for many transatlantics as well as Virgin. When flying this route themselves, I think that the A330s are used for this trip.
Not sure that either airline go over with the -300s. On a heavily loaded 753 with Pratts or even the fuel sipping Rollers it seems they wouldn't have the legs for it - particularly on the return. I await news to the contrary - I've been known to make a mistake (I once thought I was wrong)
AA operates the 752 from BOS to Manchester daily - these are not the BA partnered flights.