Here are some commercial printers I have worked with for a variety of jobs, and personally recommend. They have different specialities.
Please remember, these are commercial printers aiming at trade business (namely book, publishers or graphic designers). That is to say, not only will they expect perfect PDFs/artwork, but when costing a job, they would expect a fairly firm specification to quote to.
While everyone I’ve worked with is very helpful and generous, please be considerate of their time when asking for quotes. Do your research first and ask for staff advice if you have never worked with a commercial printer before. The possibilities are as infinite as all the different books you have seen, so firm up details such as paper colour, texture, weight, page number, run size… some may have the time to suggest the best options within a set budget.
Calverts – a cooperative in south London, they use only soy ink, so no petrochemicals.
Tompkin Press – reasonable prices, very good for smaller dimension jobs and books
Young Print - family run business in Croydon, great for bespoke finishing, fast turn-around
Identity Print – high end finishing, die-cutting etc
Team Impression – hight quality litho, digital and finishing, everything done in-house.
Bishops – a large printer in south England [no longer recommended, avoid]