Gang - can you give me some advice -

I need to fly (1 way) London to Boston around October 14th. The lowest price I can find for a one way ticket is on Icelandair for £203 (approx $370) BUT I could book r/t for $311 on US Air (depart BOS - LON on 10/8, return 10/14). Question is if I did booked r/t and was a no-show (as I definately will be) for the outbound leg can the airline cancel my itinary (i.e what is to them my return leg) ?

Or do you know any other routing / ticketing suggestions ?

Thanks much for all your help over the years.

Andy S.