Many PhD theses from British universities are available online via the British Library. The instructions below show you how to search for theses on a topic. You can use the same method to look for a particular thesis whose title you know.
Go to the British Library catalogue and enter your search words, as shown below:
Next, choose the following two filters from the options on the left-hand side of the screen, and Apply filters:
If a particular dissertation is available online, this will be indicated in the results:
Click into the record, and there will be a link to follow to read the thesis: