Fraser, you are right where we go in Italy its compulsory for 14 and under to wear a helmet and if you dont wear it you dont get on the lifts - with no exceptions.
Also, if you want to use the ski/boarder fun parks its compulsory no matter what age you are.
Buy them and then hire them to parents.
Went to Bansko last year thinking it wouldn't be expensive to hire a helmet. But they were difficult to get hold of and it cost as much to hire as to buy in the UK.
Lidl and Aldi do helmets at this time of year for about £13.00 which are up to british safety standards also Decathlon at about £15.00 why risk it? And at these prices why hire? I'm 47 and allways ski in a helmet, a small investment can prevent a major injury or worse!
Have just bought helmets for all of us. Agree with fraiser about other people on the slopes not being in control. it cost us £20 each well worth it, might be something that saves our life if we are unlucky enough to be in an accident.