More Information about Canterbury, Kent
Canterbury is a small city, population about 35,000, and is a city solely because of its cathedral and not its size. I went there in August, which is probably its busiest time, and although there were a lot of people I can't say it seemed especially crowded although the number of people did make photography a little more difficult. The centre of the city has now been pedestrianised and so is easy to navigate on foot.
There are tours available both in an open horse-drawn carriage, very nice on a sunny day, or an open-topped double-decker bus. Both, I believe, can be boarded outside the railway station. You may have to book the horse-drawn carriage in advance so find out before you go. Because Canterbury is small you can also travel by leg; I took a pair with me - very useful.
Canterbury Cathedral is one of the cathedrals in this country that make an obligatory entrance charge, whereas others 'suggest' a donation. You can't even get into the precincts (the grounds) of Canterbury Cathedral unless you pay. It is a huge place, however, and you could probably spend a day on this alone. It is, very occasionally, not open to tourists so check before you go!You can get more information from the Tourist Information Centres - they provide numerous free leaflets about Canterbury and the surrounding area.
There is a PDF Street Plan of the city which is very useful for finding your way around. It is possible to zoom in and out when viewing the document on screen and you can print it and take it with you. You can download it as a Zip file.