I'm sorry your choice of meal was not available on your flight and I hope BAEC will soon respond to you. They probably have to investigate the issue first.
However, I find your comment about a passenger next to you being "no status" and perhaps a £59 upgrade a little strange. The passenger could well have bought his CE ticket just like yourself and chosen that seat at check in. A lot of people do still check in at the airport for a variety of reasons.
And upgrades from LGW now vary in cost from route to route, starting at £60 rising to £100 each way. The AGP route is £100 each way. And upgrades are not offered unless additional catering can be arranged.