This dentist in Balham has installed a negative air pressure system and from our experience they are really understanding re: covid safety. It’s definitely worth making it clear when booking appts that you’re covid cautious. The dentists will wear ffp3 when requested but our experience with the head dentist has been best.
Here is the link to their Covid precautions- https://www.balhamdentalstudio.co.uk/covid-19-protocols/