I have heard that Tui 787 G-TUII has been into the hangers at Luton recently and has had its seating changed with the premium cabin removed at the front so now 3-3-3 as as well as the Extra space seats in the most rear cabin is due to position up to Birmingham
This fits in with seating plan that is showing BHX having a 788 operating short/mid haul for most of the week apart from one MEL rotation a week