I use driveway setts - they're small and light, cheap (less than 30p each), come in various colours, and are easy to lay to an irregular wavy edge. I just dig a shallow channel, slap em in & give a tap with a rubber mallet to make level-ish. Tesco sell a mini spirit level for about a quid that makes this kind of thing easier if ur a perfectionist. If you set them so they sit about 2cm above the lawn's soil level (ie slightly lower than newly-mown grass height) you can mow straight over and get a really neat edge. You do still have to tidy the edge now and again, but only every 5th of 6th mow instead of every time. Major time-saver in my garden. DIY stores keep em, but often worth asking a builder's merchant if they've got any leftovers they'd sell cheap. Match colour to any existing masonry, such as garden walls, driveway or house for a cohesive look. Or choose the brownest ones to 'disappear'. Use them side by side for a wide edge, or end to end for a narrow one.
You can also get green plastic edging that you slide into the soil vertically to provide an 'invisible' edge. I've never used it, maybe someone else here has...
Some people edge with log roll. It's decorative, but actaully makes edging harder imho.
If u do choose driveway setts/pavers, lay the turf 1st and let it settle in for a month. Much easier to choose the pavers' height according to the grass than vice versa. I never even broke out the spade doing my edging btw. It involved sitting on my bum on a cushion, with a just a hand trowel and my little level, and seeing how far round I could get before the vino ran out! 4 or 5 evenings of that and I was done. And my lawn's massive!!! Bx