Also bear in mind in mind York will be very busy at weekends in the run up to Christmas. We went to the York Christmas market two years ago on a Saturday and to be honest it was too busy, the impenetrable crowds spoilt it. Also forget taking a car in to centre during the run up to Christmas.
If you are travelling in by train then there are plenty of City centre hotels, but at this time of year the chain hotels cash in with eyewatering room prices. For the coming weekend the Premier Inn have a few rooms, but £299... At quieter times these would be £50-60.
I have passed the Sidings a few times, and it certainly looks interesting to anyone with an interest in railways, but you do need a car, as its quite a way out of York and if there is a bus service, there used to be, its infrequent (a few journeys per day).
If you are using the train and considering staying out of town and dont want a city centre (Leeds is also very busy in the run up to Christmas at weekends) then Knaresborough is another possibility, there are 2 tph during the day and its just under 30 minutes.
I would add a visit to Bettys tea rooms, high quality baked items and cakes, expensive but well worth it. Go and look at the mirrors with various graffiti scratched by WW2 airmen serving at RAF Linton on Ouse, many of whom never returned.