Just my opinion:
Burning holes in the sky would be: staying in the circuit for 100 hours. Or spending 100 hours flying backwards and forwards from Lydd to Le Touquet. Or getting some aerobatics training and flying loops and rolls for 100 hours. Or getting an IMC rating and flying the ILS at Bournemouth every week.
Constructive hour-building would be: staying in the circuit enough that you can land the aeroplane exactly where you want every time. And doing a few trips to France, Belgium, Luxembourg, Holland, Channel Islands and so on, but also to the far corners of Britain - and varying between large controlled airfields and small farm-strips. And getting some aeros training, or some tail-wheel training, or some float-plane training. And getting an IMC rating, and getting some actual IMC as well as taking a safety pilot to a variety of precision and non-precision approaches.
Note the important word: and. I think that variety is the important thing. It might also to help to read my CPL Diary slightly further down in this forum to see what you'll be doing on the CPL course, and make sure you're up to speed on everything that's covered.
Don't forget your 300nm trip with landings at two airports other than the airport of departure. And don't forget your night qualification, which isn't mandatory, but if you don't have it before your CPL you'll need to do it as part of the CPL training anyway.
FFF
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PS - Wish I'd had a chance to do everything on my list! But I did do most of it.