Here in Australia we aren't as lucky in our choices of wine/champagne yeast strain. Most brew shops sell a generic 'Wine Yeast' bulk packet as there are very few people around that brew wine and meads. I used the generic brand and still do because I like the result it gives me. Maybe someone else who has tried it can help you out with the Nottingham, but I don't see why it would be any different. From what I can tell the Nottingham is a very good yeast for cider so I recommend giving it a go and reporting back
One packet is enough for up to 5 gal. There is no need to split it at all, but if you go over 5 gal I would either be making a good starter or putting 2 packets in.