Just a short note to say that I just flew London (Gatwick) - Alicante (Spain) on BA. Passengers can buy upgrades onboard for 100ukp. We upgraded both ways on our trip, and it was a lot nicer than riding in the back. The flights are operated by GB airways, but all BA crew uniforms and livery. The LGW>ALC flight was on a brand new A321 and the return on a 734. We actually didnt even get charged in the end, but would have happily paid the money. If you go to the BA website and book a trip to alicante, you can get the flights for around 90ukp, and then upgrade for 100, this is a lot less than booking club europe from the start, but as soon as the doors close, any not sold seat is lost revenue, so they take what they can get.
The purpose of this post was not for trip report, but to merely share the upgrade tip.