Caruthers, it's not a case of anyone 'letting' us. Ireland used the pound, while not being in a currency union, for 58 years.
Yes, but the implications of being outside of a currency union wouldn't be great.
The White Paper explains why the SNP want to keep the pound
1. the UK is Scotland's principal trading partner accounting for 2/3 of exports in 2011, whilst figures cited by HM Treasury suggest that Scotland is the UK's second largest trading partner with exports to Scotland greater than to Brazil, South Africa, Russia, India, China and Japan put together
2. there is clear evidence of companies operating in Scotland and the UK with complex cross-border supply chains
3. a high degree of labour mobility - helped by transport links, culture and language
4. on key measurements of an optimal currency area, the Scottish and UK economies score well - for example, similar levels of productivity
5. evidence of economic cycles shows that while there have been periods of temporary divergence, there is a relatively high degree of synchronicity in short-term economic trends