The Careers Service's COVID-19 resources include links to temporary work experience opportunities.
Depending on your discipline, you could also look at online copy-editing and proof-reading, or transcription services. You can advertise your availability on portals such as Upwork (formerly known as Elance).
There may be the possibility of some temporary roles around online teaching, as with universities and schools currently moving to online teaching there is an increased demand for online provision. Some remote vacancies may also come up with Open University.
Depending on your skills, you could also consider doing some freelance coding or data analysis; as a researcher you can offer your services on platforms such as Kolabtree.