Tricky one, when I graduated a BEng was perfectly adequate and only having a BEng was never a drawback. The only reason companies want a MEng is because SARTOR changed the requirements for chartership (exemption from the engineering council exams) from three years of academic study to four years, therefore you now need an MEng or a BEng + Masters. That said I found in aerospace as a contractor I never needed chartership. Actually I would say do the BEng, if you feel you do want to pursue chartership in your engineering career (I know you want to fly, but Engineering can be reasonable way to fund the flying) you can always do a masters later on.
In my opinion someone with a BEng + an extra year in industry is far more useful than a fresh graduated MEng.
For the record only took my a day to line up an enigneering job after losing my FO job on a heavy turboprop.
So yes up to now it has been a good back up.