1. Startups can't recruit overseas students or highly skilled workers anymore without applying for a tier 2 sponsorship license. Talking about lead time of 1 1/2 months and jumping through admin hoops for approval.
2. Local students are starting school with a bigger debt due to increases in tuition fees. Now if I was a young talented programmer with a big debt (average debt of a student now is around £18K. I estimate this to increase to about £24K), the glowing lights of the city looks very attractive.