First impressions count. It is inevitable and, in my opinion, perfectly reasonable that people should decide whether or not to continue assessing any given school (or any other service) on the basis of how that outfit deals with their initial enquiry. The front-desk is the company's window to the world. If it is slack and inefficient, it's reasonable to assume that the rest of the company is as well and to take your business elsewhere.
As someone else has said, if you're in a position to spend £50,000 with a company, they should work bloody hard to get your money. After all, if you walked into a Jaguar, BMW or Porsche showroom with the same dosh, they'd be fawning at your feet! And they'll look after you with the same care for the period you need their services.
This isn't a comment on OAT specifically, but something that all FTOs should bear in mind. I do get the feeling that the past years of plenty have made some companies more than slightly complacent and arrogant in assuming that students will continue to beat down their doors. It's now a buyers' market. Use your purchsing power to get the best deal and to get the FTOs to try harder to get your business.