Recce,
I would take a look at job ads for posts in your area with experience, qualifications etc similar to yours and see what they are paying, and how this compares to your salary.
Remember to include fringe benefits though: paid training, non contributory pension schemes, private health insurance etc although you don't see the money for it on your wage slip, they do cost the employer money and are therefore worth considering in the whole context of things.
John