Hi Polince12
May I ask where are you from ?
You dont have to do high school certificate in the UK if you have one from your country.
If you want to become a dental nurse in UK the best thing you can do is to find a 'trainee dental nurse" position in the dental practice.You will work and learn at the same time ( once a week,maybe evening you will have day off to go to collage for course).
And yes most of dental practices who look for trainee will pay for your course