>I have no idea why I was upgraded from from economy on a part of my return leg, other than one hop on my outgoing trip was delayed. I was left wanting to only ever travel by business class again, even if it meant robbing a bank.
You might be being sarcastic, but just in case you're not - you will have been upgraded for exactly this reason. If you're a member of an airline's frequent flyer programme, they monitor all the flights you take and build up a profile based on where you fly, which cabin you fly in, which booking class (economy alone usually has 9 or 10 of these) and so on. BA used to expose some of the details on their web site if you were logged in if you viewed the page source code (not sure if they still do).
And yes, their tricks worked on me. I used to fly economy all the time but my wife and I booked a last minute trip to Thailand some years ago. They weren't cheap tickets - Y class I think, which is the most expensive economy bucket. Lo and behold, at the airport, we were upgraded to business. They obviously thought we could afford to pay for the posh seats so wanted to tempt us in. And it worked - a decent meal followed by a good night's sleep meant the first couple of days of the holiday weren't spent trying to recover from lack of sleep and jetlag as they were in the past.
So I now tend to pick business class. I've flown first a few times too, and while it's nice, I woudn't pay double for it. I'll still often choose economy when flying West though.