I'm afraid that linked listing of Gulfstream operators is not particularly complete.

Grumman actually put quite a lot of work and expense into certifying the G1 both for its mainstream exec role (typically 10 seats) and an airline density 24-seat configuration. I can't see one airline that bought a new one, but as they got replaced by executive jets they became an interesting and already certified option to use as an airliner.

The first ones in the UK were a handful of exec aircraft operated by large corporates like Shell and Ford (the latter had, and indeed still has, a decidedly airline-like operation across Europe from a base at Southend) so they were a known type. Field Aviation at East Midlands developed a modification to used exec aircraft to bring them up to UK airline regulations, and several were imported and modified.

Britain has a number of mid-length secondary domestic air routes, around 300-400 miles, where the main demand is morning and evening business travel by those making day-return trips and having high fares paid by their company. A key aspect is being able to do the morning and evening trips in both directions on the route with just one aircraft, without one being excessively early or the other being undesirably late and not giving a day's work at both ends, so it has to be fast and do quick turnrounds. A secondhand, high-speed, turboprop, not too large, was ideal for these minor runs, and that is how the Gulfstream 1 was operated by most of its users over here. They would tend to stand on a ramp somewhere during mid-day.

What took me the longest time was finding a picture of one of the British Airways ones on the web. Finally got there ! BA used them, contracted from multiple actual operators, on a range of the smaller commuter routes they no longer do, Birmingham to Aberdeen being a prominent one, or Newcastle to Frankfurt, and also some of the minor "Berlin Corridor" routes in their final years, Berlin Tegel to Bremen and Munster.

http://www.abpic.co.uk/photo/1036927/