In the US i've seen several instructors get jobs because an airline employee has come into the school looking for pilots on the off chance, most were freight jobs or scenic flights but one picked up a nice corporate job on a saberliner and another friend of mine got a job with North West that way. I've picked up ferry flights and ad hoc delivery freight/delivery flights because I was hanging out at the airport.
It does happen in the UK although i've never been quite so lucky personally although i've got lots of freebies which is all hours in the book.
Never turn down any job, you never know what it will lead too and it builds contacts. I've seen more than one wannabee turn down a job because they thought it was below them or it didn't pay enough only to later regret it later. If someone is willing to pay you to fly that's still better than paying for it yourself.