Marconi had two jets at its peak - one which flew every day to its Italian base in Genoa as the commercial routes took a day to get there given the schedules. No idea what type it was, but it seated about 12 and it flew from Coventry airport.
The second one did the Pittsburgh run, and was bought when BA stopped flying to Pittsburgh direct, and the change was a bit of a pain. In good old 'lack of planning' organisation, it turned out that international private jets werent allowed direct into Pittsburgh, so the private jet had to stop at Newark for immigration. I am not 100% sure but the jet was fitted out with large business class style seats only and the story was that they got a good deal on the aircraft as it was destined for Arnold Schwarzenegger, but he cancelled at short notice and Marconi snapped it up cheap. Marconi went bust about a year or so later.