National Insurance number is for tax and benefits, not the same as NHS number which is for health care ( mostly free ). I would not recommend spending money on private care, which has limited advantages such as speed of access. If you needed urgent treatment you would get it on the NHS. You may, however, have no choice but to register for private dental health care as there are insufficient NHS dentists now.
Local GPs are entitled to refuse to add patients if they already have enough, but you should be able to register with an NHS GP, especially where your husband is already registered.
This link may help :
http://www.dh.gov.uk/en/Healthcare/E...able/DH_074377
You may also consider NHS Walk-in Centres :
http://www.nhs.uk/NHSEngland/AboutNH...esSummary.aspx