Hi Adrian,

Rather surprisingly, given Volvo's reputation for reliability and solidity, that generation of S40 was the subject of quite a few recalls in its lifetime, mostly for small niggly problems but some more serious ones too, including fuel leaks. 

The general feeling seems to be that if you get a good one, they're pretty well made and reliable, but a bad one is seriously bad with problems including air conditioning pumps, haphazard central locking and immobiliser units, faulty brake sensors and more.