thanks for helping. unfortunately i don't think any of your ideas fitted the bill.
i have no date conflicts, though all are now past their requested dates. the dates in question had not been blocked and none of them were rejected by my end.
i am hoping that all this is just a language issue. It rather implies, the way its currently written, that the guest has been banned from renting my house.
The invoice reference is now defunct; I was sent an invoice for $10 or so after a client had enquired and not gone ahead. Its now dissappeared from the site.
Thanks for your help, though I wish the site had a simple contact them option.