Which model is meant for me?


C or L or T model

Since March 2000, there's a C model without mudguards, but noone has bought one and written about it on Brompton-Talk yet. The difference between L and T is:
L-model T-model
Physical no carrier rear carrier with bungees
single rear roller on a rather weak stay two rollers at either side of the sturdy carrier; they can be upgraded to in-line skatewheels ("transport set")
slightly obscured rear reflector tyre-side dynamo, rear light and reflector attached to the carrier
front light on bracket and double wiring towards it
Functional lighter can carry large packs (or even a light passenger), although parking at the same time is impossible
more stable while parked or folded
easier roll the folded package
usable but low quality lighting systems; since March 2000, high quality lighting

The main issue is the carrier. If you insist, you can add a carrier yourself (see Transporting (more) luggage with a Brompton - Adding a rear carrier to an L-model). Adding a front light and wiring yourself is easy, so they don't matter much.

How usefull is the carrier?

You can use it for Transporting (more) luggage with a Brompton - Stowing luggage on the rear carrier.

3 or 5 gears

3 speeds hubs win because they are: 5 speeds are better because they:

{Keith J Russell} [...] should we fork out the extra UKP 80 for the T5 or stick with the simpler, and perhaps more robust, T3? [...] We'll be using it for light commuting, trips to the shops, train journeys etc. Definitely won't be touring on it (yes - I kow some hardy folks do) but we'll stick with the tandem for that type of cycling. I can't imagine we'll cover more than ten miles at maximum.

Reduced gearing

In the comments below, take notice that since March 2000, 12% reduction became standard on 5 speed models.

{Clive Page, Apr 2000} Just in case anyone else is still as confused as I was about the gear options on the new Bromptons, I have here a leaflet from the Brompton Bicycle Ltd dated March 2000 which sets it out in terms I can understand (i.e. inches):
L3 & T3 47"63"84" 50 teeth x 13 teeth
L5 & T537"44"56"70"84"44 teeth x 13 teeth
C3 44"58"78" 46 teeth x 13 teeth
Options are:
3-speed models12% lower or 18% lower.
5-speed models14% higher or 7% lower.

Do I need a longer or telescopic seat post?