Welcome on board from a fellow UK ponder!
Your pond, the cladding and the decking looks fantastic, it's very professional. This surely wasn't a first project was it, you must have you done this kind of thing before? The transformation from the early pics is amazing, it's added to the value of your property no doubt. How many and what kind of fish have you got?
I changed my old and underpowered box filter and separate UV combo to a pressurised one nearly two years ago. It was not coping with the ever growing fish and their equally larger 'output'. It works brilliantly and I like its easy clean mechanism, it's a Hozelock Bioforce Revolution 9000 and it = no more stinky hands! It has an integrated UV that is 3 times as powerful as the previous one we had. What kind of filter set up did you chose?