So the gf finally got round to buying a helmet for her bike (got to set a good example for the kid now) and I have to say we were impressed by the shop assistant who sold it to her. She made sure that the helmet she got fitted her head right, regardless of cost. The fact is, the gf spent about a third less than she was willing to pay, but came out with the right helmet.
I do like it when shop assistants actually care more about making sure you've got the right stuff rather than try to sell you the most expensive thing in the shop.