TC newb: 5 Litre Bottles

[will]

I take it you have to boil the apple juice to kill any nasties?

Not if it has been pasteurised. If the bottle doesn't say then have a look and see what the shelf life is, if there's a long BBE then you can assume it has been. Also check to make sure there aren't any preservatives like sodium metabisulphate in as this can prohibit yeast growth and so will need boiling off. I've used Lidl apple juice and that seems to be well regarded for TC.