I disagree Dufwer. If you make landings at half a dozen airfields you have, by any normal logic, landed at two. There is nothing saying "two and no more than two".
Why should they question, Minty? You have signed a legal document to that effect, as you do on most of your flights. I did my official qualifier in Florida as well (since the FAA PPL qualifier has the same requirements as the CAA CPL I coud have used that, but I think it was too long ago), and never even considered proof.
If they do querry it they can easily proove you fles the aircraft from the hirer's records. That should satisfy them.