I remember Air Ops and Peach Air Tristars at Gatwick in mid to late 90's. The Peach aircraft I believe were leased from Air Atlanta Iceland with Icelandic registrations. They also operated two B737-200s G-BAZH and G-BFVB which previously were Ambassador Airways and Britannia Airways. When Peach folded the Tristars were leased or acquired by Caledonian Airways.
The Air Ops Tristars and A300s were all Swedish registered. One of their Tristars I believe ended up with Caledonian Airways with the registration G-CEAP but was never re-painted to the Caledonian livery. Because of the registration It was always referred to as "going cheap". The aircraft ended it's days at Stansted for ground handling training and was ultimately scrapped there.