Yeah, the issue is that Tsohost does not give access to Let's Encrypt on whatever plan it is we have.
I've purchased a certificate that will do 1yr for the time being, which cost about ten euros. But we should move host. If we're willing to commit to a new host for a while (like, pay three or four years up front as a bundle deal, which we do have the budget for), some of the introductory offers could save us a considerable amount of cash too.