I tend to find I usually get on the next available shuttle to MAN from LHR if I arrive early, regardless of ticket, as long as there is space.

I have not yet been told that my booking class prevents the change when I know for certain that the ticket has been a cheapo non changeable/non refundable.

My feeling is the ground staff will usually try to accomodate you in order to free up space on the flight you were originally booked and allow someone else possibly in the same situation to benefit later.

I have also had a Europe-LHR-MAN changed to a direct Europe-MAN and been op upped to CE (CE to MAN those were the days ) when I have arrived early on two seperate occasions. Although to be fair these were not the cheapest of tickets, but they were both booked in Y!

I would suggest you go for it, what's the worst that can happen

Bad Attitude