The University of Cambridge now has access to Aerial Digimap here:
Access requires registration (one-off) and login is via Shibboleth (institutional login).
Aerial Digimap is part of the Digimap Collection of on-line mapping and data delivery facilities. Users can view the data through their web browser, save the data for printing and download the aerial imagery data for use in geographical information systems.
Aerial Digimap contains aerial imagery data at scales ranging from 1:150,000 to 1:500 available for making maps online or for download. Complete coverage of Great Britain is available.
If you want to know what you can and can’t do with the maps and data from Digimap please read the Licence Agreement. There is a set of Licence FAQs if you need more clarification about what you intend to do with the maps or data.