Lincoln is really nice and a very safe and easy place to be a student. The shops are very good for pootling and there are soem nice independent shops, bars, cafes in amongst the chain stuff - and a Christmas market (normally). The castle area is lovely - if you can huff and puff up the hill!
The university is definitely quite small scale and compact - although the shared medical school ahs expanded it.
Accessible does depend where you are - it has a train station and trains direct from London have just been upped. It can be several changes of train to get anywhere meaningful , although it is easy to get to Nottingham.
The only thing I would say is Lincoln is a jewel in a backwater. Lincs itself is flat and unappealing and a bit isolated. But it hasn't bothered DS. DS was quite and insular when he started uni and now seems very sociable and used to getting around by himself.
Most of the accommodation is really nice , especially the newer stuff. The rental house market is variable.