By approved school, the airlines mean a full time integrated course, which they claim is less of a business risk than someone from a modular course.
going back over the past few years, there are people who trained at Stapleford working for BA, Britannia, Virgin, TNT, Titan, Astraeus, Ryanair, GO and a few for smaller airlines that I know of.
It probably depends on supply and demand, in times of pilot shortage they are happy to take you from a modular course.
A few of those got in with just light aircraft experience, a lot started on turboprop.