UK is(was) a net contributor - I think 12% of the budget? As a net contributor, that means there is no upside in losing the UK as a recipient, but there is a downside due to losing 12% of their revenue -12% is a lot. So there is no automatic reduction in costs, other than a few admin staff in Brussels.
So the remaining 26 have to find around 9BN. Expect 2-3BN from Germany. I'm sure Germany has this, but how to explain yet more BN going to Poland? Spain and Italy, another 1Bn each maybe? Where will this come from, Spain has 14% unemployment, 32% youth unemployment. 32%!!!
UK has 4% unemployment, anything under 5% is considered 'Full employment' - US is at 3.5%
I'm not suggesting EU will collapse, but how to explain to the southern states they have to find more money, to keep the wheels on for Germany and Poland.
Meanwhile UK gets 9BN, 6 for the NHS, 2 for Roads, 1 in the back pocket. Every year. This is around 1.2% of the governments funds. 6Bn to NHS is about 4% increase.
As to Scotland, go stay, whatever, you have 8% of the population, 5.3m, wales has 3m and is a damn site closer to the 55m consumers in england - who would build a factory or a warehouse in scotland - plenty of space still in Milton Keynes, or Skemersdale.