BY's 767-204/204ER and the later 767-304ER's were all delivered with a 2-4-2 config from new, with no premium fit.
The -204's from new were 273Y then to 290Y (reduced to 258 when they did the winter Oz charters)
The 767-304ER's had 328 seats in Economy Class, and also a later Thomson fit with 31 Premium 2-3-2 seats in the front 5 rows of the cabin that gave a total of 315 seats.
The Boeing 767-304ER fleet G-OBYA - YJ were first delivered new to Britannia Airways from 1996 - 4 of the new order did pass quickly over to the short-lived Britannia Airways GmbH of Germany.
Returning to Britannia UK, until their re-brand as Thomsonfly, then Thomson Airways, TUI Airways.
Many BY 763's also flew for sister TUI airlines - JetairFly TUIFly Belgium ArkeFly TUI Airlines Netherlands Britannia Nordic TUIFly Nordic and TUIfly GmbH.
In 1998 Air 2000 AMM took over Leisure International from Unijet and inherited their 2 newish 767-39HER's (ILFC) with a 2-4-2 fit.
The Leisure International Airways pair G-UKLH/LI were re-regd G-OOAN and AO.
AN was kept to 2013, but AO was returned early in 2001.
AMM had cancelled the 4 x A330-200's that Leisure had on order to standardise on the 767, and so AMM then ordered for 1999 and 2000 2 new 767-38AERs from GECAS in a 2-4-2 fit. No Premium cabin
afaik.
G-OOAL and AM. But both were returned early to GECAS in 2003 and 2004.
AL was later to join the TUI Airways fleet many years later in 2017, strangely registered as G-OBYK.
Renamed FCA, who now ended up obtaining early build 763's from EVA Air and Vietnam AL that FCA fitted with a low density 2-3-2 cabin with high quality seats with 33' legroom, plus a 'luxury' Premium cabin...
Merger with Thomson's came along and the TOM/FCA fleets got very fragmented, as did their configs.