I've had a lot of dealings with sort of thing. High quality note paper, technically a form of linen, does not react under ultra-violet light. Counterfeits tend to be produced on cheap paper and glow brightly. A cheap hand-held UV light is a good way of telling, i.e. if it glows, don't touch it with a barge-pole.
Best thing to do is obtain a cheap UV light and familiarise yourself with a genuine note. Counterfeits should present no problem.
This sort of thing is recommended for use, but it might be a bit big for the handbag (not that I cary one!). Smaller gizmos are available if one looks around.
http://www.uvgear.co.uk/product/product110.htm