First of all, The British isles consists of Great Britain, Ireland, numerous smaller islands and three self governing dependancies. The UK consists of England, Scotland, Wales & N.Ireland. Great Britain is the largest island consisting of England, Scotland & Wales. There are also smaller island states eg Isle of Man and the Baliwicks of Guernsey and Jersey in the Channel Islands which are self governing Crown Dependancies outwith the European Union. Phew....
Currently Scotland has its own parliament, its own legal system, education system, health service etc... so has a large degree of autonomy today. What it does not have is financial or defence independance. The Scottish National Party have a vision of a neutral, nuclear free land with it's own tax raising powers and full control of its own finances, pensions etc..
How would it affect GB or the UK ? Perhaps most serious for England, it would lose the use of its northerly submarine and airforce bases and thus weaken its defences. Scotland has a lot of natural resources - from oil to tourism and could potentially be a nett exporter of energy. In that respect, the rest of the UK would have to trade with Scotland in the same way as any other country. There is no guarantee that there would be monitary union, so you would have a Scottish / British exchange rate. There are other things too - the union flag would have to change to reflect the smaller UK. Scottish internet domains would probably .SCO instead of .UK.
Personally, I don't think it will happen and as a consolation, Scotland will be given even more powers, which ironically, is what a lot of people really want.
As for me, I don't care for haggis, but I love a dram of whisky.