Although copyright law protects all works created by someone else, UK law makes provision for you to use these works for the purposes of your own study, within reasonable limits, under an exception to copyright law known as Fair Dealing. More information about fair dealing exceptions, and how to use these legally, can be found on the UK.Gov website, but the two most relevant exceptions are:
Copying for Research and Private Study
Students and researchers will often need to make use of materials which are copyright protected. In the context of your studies, you may have to make copies or use extracts of those materials. This is covered in UK law by s.29 of the CDPA, which permits making single copies or taking short extracts of works when the use is made for non-commercial research or for private study. The exception for research and private study applies to all types of copyrighted work, and to recordings of performances of works. However you are only allowed to copy what is necessary for your purposes and could be considered to be 'fair' - copying the whole work or making multiple copies of a chapter/section would not be considered fair dealing.
Copying for Quotation, Criticism or Review
When writing an academic essay, dissertation or thesis, or doing most other kinds of academic research, you will almost certainly want to quote from copyrighted works. This is permitted under s.30 of the CDPA, so long as your usage can be said to be Fair Dealing and the extracts you use are no longer than required to achieve your purpose. This is allowed for any type of copyrighted work, including images.
You must also include sufficient acknowledgement of the original work, to identify the creator of the work and the title of the material. In practice, this is done with proper referencing and citation – which is a copyright requirement as well as an academic convention.