Bejesus, Sage buys Protx, renames it, and manages to infect it with Sage's usual lets-make-this-really-hard-to-use ethos.
Note the instruction to "click proceed to complete your payment". You see any button labelled 'proceed'?
No, nor do I.
Most people will, probably, click the right arrow button to proceed. But some won't. Maybe 5% won't? That's 5% of customers who you have already paid to market to, you've already guided through your site to buy something, but who abandon because the guy that wrote your hosted payment page couldn't be bothered to check his text / buttons properly.
Still using a desk diary to manage your guesthouse reservations?
Try KeepMeBooked: simple web-based reservation management