As a BMI flyer and "used" to their way of operating with regards change, I have seen a very subtle change over the last couple of weeks (at least on LHR-BRU).

That is that the "Discounted" Economy fares are only available for more than 2 days ahead. This is only based on observation as there are no tickets below £142 for tommorrow and wednesday. Indeed I saw the same last week.

The consequence of this is that if I book the £32 ticket on Thursday (Today) if I do change it to another flight after today then my minimum upgrade with be £110 + £25(Very SNEAKY).

I don't know whether they are adopting this poilcy on other routes but it is something to watch out for