It's rather irritating that on some routes BA's European fares that are semi flexible specifically prohibit changes on the day of departure - These aren't cheapy fares but D,C,H or B class has this rule as well .. You can't even pay to upgrade to a fully flexible ticket on the day of departure.

CHANGES BEFORE DEPARTURE CHARGE GBP 30.00. NOTE - UPGRADES PERMITTED TO ANY HIGHER FARE AT A CHARGE OF GBP30.00 PER TRANSACTION PER PASSENGER PLUS ANY DIFFERENCE IN THE FARE. CHARGE APPLIES TO ADULT AND CHILDREN ONLY. CHANGES ONLY PERMITTED UP TO DAY BEFORE OUTBOUND DEPARTURE. NO CHANGES OR UPGRADES PERMITTED ON DAY OF DEPARTURE.

This applies mainly on the German routes where the fares are all xNCLON2 fares. On these routes I think it's only the YFLBA / JFLBA fares that seem to be genuinely flexible on the day of departure... Which is fair enough as they're the expensive ones ... but it's fairly annoying that you can't upgrade a £400 ticket to a £500 ticket on the day in order to get flexibility if you need it.

It seems that if you were travelling to Munich on a CNCLON2 fare for the bargain price of £508+tax r/t and you were able to catch an earlier flight back the only thing you could do is ditch the (non refundable) return portion of your ticket and buy a totally new one way ticket back to London ... seems a bit harsh

Annoying thing is many corporate TAs sell the semi flexible tickets as being flexible and people often get caught out trying to change them (usually if a meeting finishes early and trying to get on an earlier flight back.)