We have assembled a unique dataset of deep near-infrared images of 3 statistically matched samples of radio-quiet quasars, radio-loud quasars and radio galaxies in the redshift band 0.1 < z < 0.3, on the strength of which we have recently been awarded 35 HST orbits of WFPC2 imaging in Cycle 6 (- the largest single HST award made for quasar hosts). We therefore propose to ensure that the final ISO database contains mid-IR to FIR continuum measurements of all visible targets in our 3 samples, which contain a combined total of 48 sources. Thus we request 77604 secs (or a reduced allocation of 46412 secs - see OBS_SUMMARY) to observe the 22 AGN not included in current open-time or guaranteed time proposals (which are visible during the remainder of the ISO mission). We stress that we are the only group to have undertaken a study of the symbiotic relationship between the nature of the AGN and the host galaxy in quasars and radio-loud galaxies, using carefully selected matched samples. We are also the only group to have obtained HST, ground-based optical (KPNO 4-m, WHT), infrared (UKIRT), submm (JCMT) and radio (VLA, MERLIN) images of matched samples of radio-loud and radio-quiet AGN for this purpose, as well as off-nuclear optical spectroscopic measurements to combine with our latest stellar population synthesis models. Hence we are in a unique position to perform a rigorous test of unified models for radio-loud sources, to determine the extent to which the different host galaxy morphologies (disc or spheroidal) of radio-loud and radio-quiet AGN vary in terms of stellar mass, dust/gas content, spectral energy distribution, star-formation history of the host galaxy and the immediate environs.