Definitely second this. Doing the harder option and taking my CBT on manual. Will take the instructors advice too as I only intend to ever keep an automatic bike, but would like the manual licence there should I ever need it or change my mind.
Btw do you think a novice like me would find it somewhat easy to adapt to a maxi scooter especially in the streets of London?
My reasoning for doing it on an automatic was that I had already decided I was going to get a scooter for practicality and wanted to get on two wheels quickly, so I did not want to risk the prospect of not taking to the bike's method of gear changing. Or potential challenges of adapting to an auto, for that matter. In both cases I may have been worrying over nothing but it is in the past now.
I can't comment on the streets of London but, bearing in mind that you would be restricted to a 125 and not a true maxi as such, I don't think it would be that difficult. Ideally spend some time on quiet roads to get used to it but (albeit without spending time on a geared bike), I went from no motorised two wheeler experience to doing CBT on a 50cc auto to riding a 125cc by myself, in the space of a week or so (I did end up hitting rush hour a bit too soon, to be honest, but I lived to tell the tale, in spite of some cringeworthy mistakes). I have driven a car for around 10 years as well though, which I think helps a great deal as you can spend a bit less time worrying about things like which lanes to use and more time learning how to control the bike.
Main things I don't like about an auto relate to low speed maneuvers. The throttle alone does not always seem sufficient to maintain a low enough speed in slow moving traffic and just using the brakes seems like a crude solution, compared with using the clutch in a car to control speed. You also do not have the option of using the clutch to disengage the engine if things go wrong.