Why does LGW have two versions of the 777? 77S and 77T. The seating count is identical apart from one has 4 more WT+ seats than the other.

I've just fallen fould of this as had the legroom seats book in Y for a trip to Aruba. It's been changed for the other type, and they've shifted us to the middle of the plane. Luckily I've managed to get back into the legroom seats, which has a different row number.

Seems a strange system to have when it's a relatively small longhaul operation. I know seat layouts isn't probably high on the list of things an airline should be concerned about, but it makes an important part of the holiday booking process for customers.