Thanks for your reply Phil L, the firm that did the job did exactly as you
said, as it turned out only two holes where needed as the orig back door
opening ( now inside but 1mtr from the new outside wall ) meant they could
fill one section from the outside edge. The holes in the outer walls are now
almost invisible. I know it's warmer weather now but I'm sat here at nearly
midnight having had the heating switched off for two days and its really
warm inside, the drafts are def reduced if not gone altogether ! they also
replaced the airbricks under the suspended wood floor areas with sleeeved
one's and put what looks like a 20ft long loo brush vertically in the cavity
between our half and the neighbours ( 1930's semi ) so it didn't spill over
into their walls. We paid £75 and Powergen paid the rest ( or prob the
government paid Powergen ) but so far it looks like the heating bill for
next winter will be lowered.

Pete