At the moment, the main reason why English students are not all going to university in Scotland (where university tuition is free, compared to English universities that will typically charge £27,000 for a 3-year degree) is that Scottish universities charge them up to £27,000 for their degree. This is only possible because the EU rule about not discriminating against EU students only applies to students from other EU countries (such as Ireland, Denmark or Bulgaria) and not to students from other parts of the UK (England, Wales and Northern Ireland).
As soon as Scotland regains her independence, rUK students become EU students and will have to be treated in the same way as students from Scotland.
However, some lessons can be learnt from Scandinavia. Denmark in theory has to treat Swedish students the same as Danish ones, but this is not the whole truth.
Denmark used to have a big problem with too many Swedes studying medicine in Copenhagen and then going home after graduation. In 2007, Denmark therefore did two things (link in Danish): (1) They changed the number of advanced highers (“højniveaufag”) a student needs to pass to get a grade top-up, which benefitted Danes in comparison with Swedes. (2) They changed the way they translated Swedish grades into Danes ones (that is, they made it harder for them to get in).
Apart from this, Denmark pays generous grants (typically £7616 per year) to university students who are either Danish citizens, have lived in Denmark for five years prior to starting university, or who have parents that are EU citizens and have moved to Denmark for work reasons. Other students don’t get a penny.
Scotland could copy some of these policies after independence. There are already plenty of differences between A Levels and Scottish Highers to provide opportunities for tweaking the entry requirements to make it harder for English students to get into Scottish universities (the brilliant ones would of course still get in, but that would be to Scotland’s advantage anyway), and Scotland could introduce tuition fees for everybody, but cancel out the effect by creating grants for Scottish citizens and long-term residents.
In an ideal world such measures shouldn’t be necessary, but until it dawns on the English that they’re shooting themselves in the foot by pricing bright young people out of universities, I fear that Scotland will have to take a leaf out of Denmark’s book.
Update (May 2013): Denmark’s rule about only giving grants to long-term residents has been found unlawful by the EU Court of Justice. Now everybody who has moved to Denmark in order to work (even if only for the summer holidays before starting university) has the right to get Danish grants when studying in Denmark.