Wylex or Volex
Was called Sector GE iirc - they want a kick in the backside if they can't get parts for a CU they were still supplying last year! We got some with RCD incomers with L marked on them, only problem was it was on the side which connected to the neutral rail
Funny you say that cos I had a feeling their own brand cack was GE, (myself I've always installed wylex cos it's so common round here.)