"'Fitting out' of (some) stuff being done at Blackbushe. Well, one of 'em is there, at least."
Not correct. The one at Blackbushe is a B200GT for SERCO/45 Sqn at Cranwell (the first of 2 new ones).
The ones at Hawarden are the four B300s that the original poster alludes to. These are more like USArmy Guardrail types than the multi-engined trainers operated from Cranwell.
There are 2 distinctly different orders/requirements.