You can be as sensible as you like, the fact is as its being used for business purposes you have to have a certificate for it, its a 3 day course dealing with the safety and maintainence side of things as well as logging. A farm locally here had this as one of their failings and ended up with a fine over ?100,000 from HSE.
This is what HSE says:
http://www.hse.gov.uk/pubns/indg317.pdf
To my mind a chainsaw is the most dangerous piece of hand held kit there is,myself and many others think the sale of them to people without some form of training should be prohibited. Would you know when the chain and bar is worn beyond tolerances without the training?