You can now find all issues of INTERIM magazine by YAT here on the HER website.
The issues span from 1973-2001 and contain a variety of articles on excavations across the city, conservation and research projects. Unfortunately, there is no one single index for the volumes but there is fun to be had in 'flicking' through them individually.
Many of the main excavations covered have been linked to the relevant HER Event so you may have stumbled across some articles already such as the North St Pumping Station (1993) or at 41 Piccadilly (1992).
To jump straight to the source records and browse for yourself you can use the links below. There are 4 magazines for each series of Interim.