It's really up to him what he does in his own time. It's his own responsibility to understand and abide by laws, and at the same time can have no complaint if he's pulled up for it. He is on here, so he may wish to comment, but then again he might not?

An enthusiasts forum obviously cannot enforce the rules, but we can point to them: https://www.gov.uk/guidance/national-loc...ay-at-home.
If anyone is that bothered about it, you can seek support here: https://www.police.uk/tua/tell-us-about/...-measures/

Stay safe and be responsible.