Problem: you save 50p coins (or whatever coinage you save) and you have a whisky jar full. You know your bank won't take them and you hate paying 8.9p in the pound to use those Coinstar machines in supermarkets.
Solution: Use the supermarkets own self-service machines instead: buy a small item (e.g. Freddo the Frog chocolate at 20p) dump your coins into the self service hopper plus 20p and out comes crispy notes and 0% fee.
I tried this tonight in Morrisons with £10 in 50p's and got a £10 note. I wouldn't recommend dumping a whole whisky bottle though. I'm planning to take 20 quid in change per visit (maybe best avoiding busy times).