"Like most UK clubs,
we have fairly strict currency requirements, so I would expect to take a
checkride if I haven't flown for a month or more, despite having been a
solo pilot for 20 years/620 hours."

Not the culture down the road at Dunstable - experienced solo pilots are never required to take a checkride, and would not very often request one. The only requirement we impose is an annual winch check for those wishing to take winch launches.

What did you do after lockdown? We were not flying dual at that stage, so solo pilots all flew after the lockdown layoff (was it two months?) without any checkrides.