The two following websites permit to search, and in some cases, access the full-text of several university theses in the UK and Australasian areas.
EThOS is the Electronic Theses Online Service, associated with the British Library. The databases contains 250,000+ theses, prepared in British universities. No login is necessary to search the databases but a (free) personal account is needed to download a theses or request its digitization. Payment of fees may be required.
The Australasian Digital Theses Program wants to establish a distributed database of digital versions of theses produced by the postgraduate research students in that geographical region. About 40 institutions participate. No login is necessary to search abstracts or access full-text when available. Some institutions may ask for payment to access full-text.
To search more theses from the US and around the world, you can also use the ProQuest Dissertations & Theses database, provided by the USF Libraries.