I have been using that NHS dentist for a few years now and never had any problems with them, they have always been very friendly and helpful. I know the front of the building doesn't look very nice but don't let that put you off. I am not sure if they are taking on new patients at the moment as I think they were working through a backlog of appointments for existing patients, but it's worth giving them a ring to find out.
Alas they are no longer take new NHS. We tried another in Upper St again no longer taking new patients. We will stay as we are until whenever we get a government genuinely dedicated to the NHS including eyes and teeth and Care. Thanks for your reply Richard