Query on UK visa options for South African postdoc at Birkbeck University funded by a South African organisation
Unfortunately, short of marrying an EU national, you likely do not qualify for a UK visa and there is nothing that can be done about this. This document contains the information about salary thresholds. These apply strictly, there are no exceptions. Even if your position fulfils a shortage occupation the salary threshold still applies. You will need to find some more funding, or give up on taking up the fellowship in the UK. You may also consider contacting the university to see if there is anything that can be done to help your situation.