Adopt the brace position!
Both paths share similar skill sets as required by the job, and also different 'specific' skills as dictated by the unit you work at post-college, hence why each unit requires it's own training plan and validation. (Mil traffic operate differently to civil, etc).
No unit has the same airspace/traffic/restrictions etc so leaving the ATC college, whether it be RAF or Civil, will not make you eligible to walk in to a unit and be able to work the traffic in a safe, orderly & expeditious manner. You merely leave the college with a licence to learn at the unit you're posted to.
Airprox's can, and do, happen at any unit, regardless of where the staff were trained, so to imply those trained at Shawbury may not be up to the standard to work Northolt is absolute bolleaux. It's a challenging job wherever you were trained, and wherever you're posted.