Dr. Cassidy has worked in a large number of hospitals since he qualified in 1978. These are listed below:
- Glasgow – Glasgow Dental Hospital, the Western Infirmary, Stobhill General Hospital, the Victoria Infimary.
- Lanarkshire – Monklands General Hospital, Airdrie, Law Hospital, Carluke, Stonehouse Hospital, Hairmyers Hospital, East Kilbride.
- Northumberland/Cleveland/Cumbria – Newcastle Upon Tyne Dental Hospital, Newcastle General Hospital, Sunderland General Hospital, Middlesbrough General Hospital, City General Hospital, Carlisle.
- Yorkshire– Leeds Dental Hospital, Leeds General Infirmary, Hull Royal Infirmary, Westwood Hospital, Beverley, Huddersfield Royal Infirmary, Pinderfields General Hospital, Wakefield.
- London – Eastman Dental Hospital, Kingston Upon Thames General Hospital.
- Jersey – Jersey General Hospital, St Saviour’s Hospital, Overdale Hospital.