Marylebone always feels like it's from a bygone rail age and, like Paddington, is filled with the (to me, lovely) sound of rail engines idling. One fault is that the Harrow train (destination Aylesbury) is often hidden on Platform 6 which is that bit further away from the concourse. Worse, there are usually two trains on the platform and the one furthest away is the one you need. Often they give you less than 10 mins notice which is fine for me but was an awful burden on my poor dad who really struggled to get to the train in that time.
Just outside the station you can get the 2 (goes to Victoria) or 205 (goes to Stepney Green / Bow) bus and if you cross the road there's the 453 to Deptford Bridge. There's also a normal-priced newsagents shop there if you want refreshments for a longer journey (Marylebone goes to Birmingham, Oxford (as of 12 Dec 2016), Warwick etc).
Anyway here's what England, their England has to say about the station and a journey to Aylesbury (written in 1933 by AG Macdonell, set in the 1920s).
"Two days later he was at Marylebone Station, quietest and most dignified of stations, where the porters go on tiptoe, where the barrows are rubber-tyred and the trains sidle mysteriously in and out with only the faintest of toots upon their whistles so as not to disturb the signalmen, and there he bought a ticket to Aylesbury from a man who whispered that the cost was nine-and-six, and that a train would probably start from Number 5 platform as soon as the engine-driver had come back from the pictures, and the guard had been to see his old mother in Baker Street.The full text is available at Project Gutenberg Canada.
Sure enough a train marked Aylesbury was standing at Number 5 platform. According to the timetable it was due to start in ten minutes, but the platform was deserted and there were no passengers in the carriages. The station was silent. The newspaper boy was asleep. A horse, waiting all harnessed beside a loaded van, lay down and yawned. The dust filtered slowly down through the winter sunbeams, gradually obliterating a label upon a wooden crate which said "Urgent. Perishable."
Donald took a seat in a third-class smoker and waited. An engine-driver came stealthily up the platform. A stoker, walking like a cat, followed him. After a few minutes a guard appeared at the door of the carriage and seemed rather surprised at seeing Donald.
"Do you wish to travel, sir?" he asked gently, and when Donald had said that he was desirous of going as far as Aylesbury, the guard touched his hat and said in a most respectful manner, "If you wish it, sir." He reminded Donald of the immortal butler, Jeeves. Donald fancied, but he was not quite sure, that he heard the guard whisper to the engine-driver, "I think we might make a start now, Gerald," and he rather thinks the engine-driver replied in the same undertone, "Just as you wish, Horace."
Anyway, a moment or two later the train slipped out of the station and gathered speed in the direction of Aylesbury.
The railway which begins, or ends, according to the way in which you look at it, from or at Marylebone, used to be called the Great Central Railway, but is now merged with lots of other railways into one large concern called the London, Midland and South Coast or some such name. The reason for the merger was that dividends might be raised, or lowered, or something. Anyway, the line used to be called the Great Central and it is like no other of the north-bound lines. For it runs through lovely, magical rural England. It goes to places that you have never heard of before, but when you have heard of them you want to live in them—Great Missenden and Wendover and High Wycombe and Princes Risborough and Quainton Road, and Akeman Street and Blackthorn. It goes to places that do not need a railway, that never use a railway, that probably do not yet know that they have got a railway. It goes to way-side halts where the only passengers are milk-churns. It visits lonely platforms where the only tickets are bought by geese and ducks. It stops in the middle of buttercup meadows to pick up eggs and flowers. It glides past the great pile of willow branches that are maturing to make England's cricket-bats. It is a dreamer among railways, a poet, kindly and absurd and lovely.
You can sit at your carriage window in a Great Central train and gallop your horse from Amersham to Aylesbury without a check for a factory or a detour for a field of corn or a break for a slum. Pasture and hedge, and pasture and hedge, and pasture and hedge, mile after mile after mile, grey-green and brown and russet, and silver where the little rivers tangle themselves among reeds and trodden watering-pools.
There are no mountains or ravines or noisy tunnels or dizzy viaducts. The Great Central is like that old stream of Asia Minor. It meanders and meanders until at last it reaches, loveliest of English names, the Vale of Aylesbury."
*An almost identical journey (running on a parallel line, though sometimes they run on the same tracks) is the Metropolitan tube line from Baker Street a few minutes walk away from Marylebone, that takes about ~20 minutes. Euston runs a rail service to Harrow & Wealdstone and Hatch End etc. The Overground trains also go from various North Central London stations to Harrow & Wealdstone but that's a slow stopping train.