[Loz]

Can't help you with this, Martin, other than perhaps to suggest seeking a restraining order on the collection agency, preventing them approaching your friend's rented property.

As an aside, I don't know whether the law has changed recently, but where a business has a lease with a landlord, the landlord was legally entitled to seek payment of arrears from previous business tenants from the current tenant. I think that arrears of unified business rates could also be claimed from the current tenant by the Local Authority. Weird stuff, that.

Hope it gets sorted.