The quintessential London commuter IMO is any of the Condor singlespeeds – Pista being the real classic or a Tempo if you’re middle-aged (it takes guards and a rack). It helps that they’re lovely bikes to ride.
Wibble I think Graham Weigh and Dolan names are interchangeable these days. I run 23mm but there is loads of clearance for a wider tyre. I run sks narrow gauge mudguards for long TT’s! The welds on the frame aren’t brilliant but it’s serviceable.