The really sad and worrying thing is the ignorance of the realities of pilot training by some in ATC. Until the Multi-Pilot License is introduced, those flights in "PA-28's", in this case light twins but "spam cans" nevertheless, are the final stages of pilot training before the candidate becomes a commercial pilot. To keep the airlines supplied with "heavy aluminium tube" drivers these flights have to take place in and out of controlled airspace. The CAA insists on it.
And by the way, Cardiff ATC have long since dispensed with the the "PA28 clogging up the hold for an hour?....." They accept no light aircraft for training.