You have to check all the different programs, i am with KLM/AF and have about 60000 miles, i was flying with them every month and gaining about 6K per month until i moved locations, now i travel on a variety of airlines so my airmiles are not building up with any specific carrier.
with BA i think you collect 1,400,000,000 and you get a free pen
not too sure what you mean about the 150 pound thing though.
Simon