I wholeheartedly agree with Shunter because General Aviation is so expensive in the UK that this is likely to be your only opportunity for 30 years to fly for pure fun! Go for a tour of the country. Do a cross-channel trip. Go to the USA and fly there. Join a Flying Group and do all the fly-outs. Take your family and friends on flights.
But if you insist on being conscientious, have a look at the link to the CPL course provided by BHenderson and see whether there's anything in the course that you can practise in the type of aircraft in which you will be doing your hour-building. IMHO there won't be much point perfecting your CPL Airwork or Instrument flying in a 1982 vintage C152 when your CPL will be on an Arrow with wobbly prop and retractable undercarriage...
What you can practise is navigation, including tracking a few beacons using the ADF and VOR. Don't do it on every flight, but occasionally try it. I toured Kent on one flight, tracking all the coastal beacons. It got boring...
But generally speaking the key flying skill for the CPL is
accuracy. Accord every approach and landing the respect and care it deserves, fly the numbers when climbing and descending, and try to fly straight and level when you're trying to fly straight and level! Oh please adopt correct Radio Phraseology!
