I've just bought an Africa Twin for exactly that commute (M40, A40, West end). I knew it'd be a bit wide before I bought it, but I want to do some long-distance touring next year and it'll be up to the job. Having done the run a few times now I'd say go with the thinnest bike you can that's still a laugh/comfortable if you want to get there quickly. There's so much traffic that proper hooning only occurs about 20% of the journey.
But it's still a million times better than taking the f'ing tube
