Further to Spotit3 and Bobbisox's posts, liquids are permitted in hold luggage but it's often considered wisest not to put aerosols into your suitcases. That's because the lower atmospheric pressure in the hold at altitude increases the pressure difference between the inside and the outside of the can, meaning that there's a possibility of the can rupturing and depositing its contents into your suitcase.
Unless 237SJ has extremely small cans of hairspray, she is acting illegally and can expect some severe delays (and the confiscation of her hairspray) when she attempts to pass through security checks. Apart from baby foods and liquids required for immediate medical needs, no liquids can be taken into the cabin of any aircraft flying out of any EU airport unless they're in quantities not exceeding 100ml:
http://www.direct.gov...avelintheUK/DG_078179
The only exception would be if the liquids were purchased after passing through the security check.
Chris.