Hi John
My reading of the NHS guidelines suggest that you are right and it should still be coverered. It does say
Band 1 course of treatment
£16.20 - This covers an examination, diagnosis (eg: x-rays), advice on how to prevent future problems, and a scale and polish if needed. Urgent treatment when you need to see a dentist immediately also costs £16.20.
But that reads to me that it is also covered and NOT an extra £16.2. I would call NHS direct and ask their advice as I think you have been wrongly charged (on what you have told me) but they should know for certain NHS direct Number: 0845 4647 or http://www.nhs.uk/NHSDirect/Pages/nhsdlanding.aspx (http://www.nhs.uk/NHSDirect/Pages/nhsdlanding.aspx)
BR
Jon