If you're able to use a grater, peeler, and knife, then it probably isn't worth paying more to have your cheese grated, your fruit diced, or your vegetables peeled and cut in advance. You'll save a pretty packet by buying them whole or in a block.
Comparison: Essential Waitrose Lighter Mature Grated Cheese costs £2 for 250g (that's £8 per kg) while Essential Waitrose Lighter Mature Cheese costs £3.50 for 550g (that's about £6 per kg).