All diving / recompression chambers in the UK are either:

• Independent charities
• Privately owned based in NHS hospital grounds
• Privately owned based in private hospital grounds
• Privately owned based outside of hospital grounds altogether

There is no such thing as "an NHS chamber", however the NHS does "fund" treatment for decompression illness if the diver is:

• A UK citizen
• A non-UK citizen but with residential rights in the UK

DAN / UK-based dive insurance becomes invalid once the diver has returned to the UK, i.e. it can only be used if the diver is abroad, however a non-NHS entitled diver's insurance will be valid for treatment in the UK.