The EThOS service is currently unavailable a result of a cyber-attack. Updates on British Library services are available via their blog.
Whilst the British Library is working to restore access to EThOS their online catalogue now provides access to digital doctoral theses held in UK institutional repositories - Using Advanced search and selecting 'Theses' from 'Material Type' dropdown menu is recommended. To access these documents, search for a thesis and then click on a title of interest to view the full details for that work. The link can be found under the section labelled "View Online - External Resource Available" (in green) just above the "I want this" section (in red) at the bottom of the page.
See the following examples of finding theses that are available (Available Online in green with a link to the thesis) and those that aren't (red box with 'This item is not currently available' text).
Available thesis
Unavailable thesis
EThOS (Electronic Theses Online Service) provides access to UK doctoral theses from The British Library, in association with higher education institutions in the UK. Most available theses are PhDs, but also other types of doctoral thesis, e.g. D.Ed., Mus.D., D.Eng (for M Phil and other theses contact our Get It For Me service).