The Library stocks books on writing dissertations and research skills. Please search Discover (you can filter your search to Print Book and/or eBook in the 'Format' options on the left of the results page).
You will find lots of research methods books on Discover, with useful information on why you might select a certain approach and how best to work with the data.
There is also a special service called Request It! If you need a book or journal article that we don't have in stock, the Library will try to locate a copy for you to access. You can request an item using Discover and there are instructions on how to do this here: FAQ: How do I request a book or article not held in stock?
There are also resources on writing a dissertation available on the University's Skills for Learning website.