I have just recently paid £194 to have a new set of dentures made - I have been back many times over the last 3 months and they still do not fit - can I get a refund from my dentist!!

You got a bargain for your new dentures! Here in Canada you'd be paying closer to $900.
All you can do is ask your dentist if he'll refund your money. It's not uncommon for adjustments to be needed when you get new dentures.