Thanks for your replies. I'll be commuting into the centre of London, most of the journey will be on road. I've never ridden this far, or on road before, last time I road was as a kid but was using the pavement.
I'd say i'm in good shape, i'm 6ft very lean and do quite a bit of exercise throughout the week.
I like the idea of the fold up Brompton, but yes they do have small wheels and don't look very suitable for long distance.
Bromptons are great bikes. Some find them ugly, others find beauty in their design. Those that love them will tell you that you can tour the world on them....and you can. Thing is, you could tour the world on a chopper if you were motivated to do so.
In London, bromptons are pretty trendy and seem to be the weapon of choice for those who commute by train and want to gain some fitness by riding from a station rather than taking a bus. They also are "allegedly" big in the world of architects and creatives.
If you plan to ride every single day I would say a Brompton is over engineered for you, you will be paying for stuff you don't need...like its fold ability. If you plan to break the ride and occasionally take the train, a Brompton is perfect .
I ride anything from 10-20 miles into work (and the same back) but not every day. I ride a standard (I hope she never hears me refer to her as that) road bike. It's perfect, fast, zippy and capable of taking me much further afield at weekends ( she carried me from Brussels to Paris last weekend).
If a full on road bike is not your thing, look at hybrids that will take mudguards and panier racks....they are basically road bikes with a few extra brackets and flat bars.
Another alternative is a single speed or even a fixed bike. These are super trendy in London, if you work in the arts, graphics, computer or creative world, you will not be allowed to ride anything else...it's the law.
Single speed and fixed bikes have no gears and often no brakes (other than the chain stopping the rear wheel) whilst this may sound mad, they are extremely responsive and offer a genuine low maintainance option. I am considering one myself right now for the winter muck.
I suspect ( and please don't take this as an insult, we all do it) that to start with you will choose a bike with far too much stuff on it, brackets, mudguards,mirrors, etc and eventually will find, through experience, that these are just a preference, not a necessity. Ultimately you will trim down.
The same goes for the stuff you carry.
When you start you will carry more luggage than a Kardashian on tour but one summers day will find yourself happily spinning through London with nothing more than a spare tube and a tyre lever....or two.
Good luck, hope that helps, if you are new to getting about town, we have a guide for new city riders, that we made especially for you, it's a sticky at the top of the commuting section.
https://www.cyclechat.net/threads/the-essential-guide-for-new-commuters.56622/
J