To think £790 for a crown and 2 fillings is a ridiculous amount of money?

[HoHa]

I need one of my back teeth crowned (multiple cracks and bits falling off) and the teeth either side filled. I see a private dentist and pay monthly into a dental plan, so this quote includes a 20% reduction for being part of the plan.
My family have been seeing this dentist for around 5 years after several disastrous years seeing an NHS dentist (who has now been struck off I believe) He seems excellent and I know that private is more expensive than NHS - but nearly £800! I'm in shock.

Sounds about right to me, maybe slightly high but would say £400 for a crown and £100 per filling would be reasonable. Some dentists do CAD- CAM (cerec) crowns and filings so all finished in one day and this can be more expensive still.
Dentists are highly trained professionals, assisted by another trained professional and dental materials and lab bills are very expensive. Only in the UK do people expect Dentistry to be cheap (due to the NHS) the rest of the world accept that it isn't.

I had two crowns done (privately) 2 years ago -£1100 for the pair...so yes you're not paying over the odds...however I was(and continue to) pay into a private fund -£25 per month for me and DH which totally covered the cost plus 2x check ups/other work etc annually. Sounds like your plan (whilst in theory a good idea) isn't particularly worthwhile. Definitely worth reading the small print before signing up.