[Kymmy]

If you get a wideband over an identical group A then the gain figure will be lower and also you're more likely to pick up interference from higher up in the band..

Also you mentioned an amp in the loft? is this a decent low noise amp that is masthead mountable?? or a cheap one??

Also if you haven't already get some decent co-ax as poor co-ax can attenuate the signal more than most people realise