Gingernut... excuse me be slightly pedantic, but as you're interested you might accept my minor correction to your terminology. There are no "Upper Airways" above Manchester. In the UK airways are only established in the middle and lower airspace, Above FL245 (currently but about to change) slightly different rules apply, in that that all airspace is regulated so there is no need to established corridors, therefore you only need "Upper Air Routes"
Increasing amounts of traffic these days is "off route" (especially at off-peak times, but probably not over Manchester I will admit)... but that's a whole new topic?