The problem with buying the cheaper AP single tickets - either from London or Manchester - is, of course, that if your flight is delayed and you miss your train, you are screwed.

Are you going one way or return? If you are going return Manchester-Grange, the cheapest walk-up fare is an off-peak return of £28.90, which is not too bad compared with £18 for two AP single tickets. In one of the many perversities of the rail ticketing system in Britain, this "off-peak" fare is available on any train. The only difference from the more expensive "anytime" return being - in this case - that you are not allowed to break your journey. Definition: "Break of journey is not permitted except to change trains at an intermediate station or to access station facilities."

[This is highly unusual - there are normally time restrictions with off-peak tickets, as you would expect from the name].