Hello Alison
In answer to your question, you cannot DEMAND treatment from your dentist, and in a similar way, a dentist cannot INSIST that you have treatment if you do not consent to it.
Under NHS guidelines, a dentist has a duty of care to provide treatment that it deemed neccessary to secure and maintain oral and general health. However treatment that is purely on cosmetic grounds would not be included.
When formulating a treatment plan for a patient, this would normally be done in a series of steps:
1) History taking
2) Examination
3) Tests and investigations
4) Diagnosis
5) Treatment plan
Sometimes these steps 'overlap'. The treatment plan should be discussed with you, adjusted if needed and then consented to.
A routine examination would normally include a 'Basic Periodontal Examination' (BPE) to assess and monitor the health of the periodontal tissues (gums). A series of figures are recorded ranging from 0-4. Unless you score 0 in all areas of your mouth, treatment is usually indicated. This can range from simple advice on cleaning to scaling and more complex treatments.
Hope this is of help to you. I would suggest that your best option is to discuss the matter with your dentist again.