In 1963 Gillham worked as a Staff Tutor in the Biological Sciences at University College of South Wales and Monmouthshire, Department of Extramural Studies. Here she lectured on numerous occasions for numerous courses, some examples including; a series of Travel Talks in 1963 (Tuesdays from 8–8.30 pm, for 11 weeks from 15 January to 9 April, and Fridays from 7-9pm), seven lectures on Coastal Vegetation in 1963, and 20 lectures in the course titled 'Environmental Studies in Natural History'; the latter being an annual course between 1970 and 1974. She gave her Extramural lectures in a range of locations in Wales including; Cardiff, Merthyr Tydfil, Abergavenny, Risca, Llwynypia, Pontypridd, Gwaelod-y-Garth, St. Donats, Bargoed, Hay, Bridgend, Barry, Cowbridge, Porthcawl, Bassaleg and Llantwit Major, mostly on topics of botany and natural history. Gillham also led numerous study tours for her students in locations closer to home; Guernsey (1969), the Shropshire Hills (1970), Monmouthshire (1970), Skomer Island (1978), Norfolk (1986), the Heritage Coast (1987), Gower (1987), Merthyr Mawr (1988), and Scilly Isles (1988), as well as further afield; Corfu (1969), Sardinia (1985) and Portugal (1986).