Irrelevant?
Please back up your argument with more than just claiming that the state of financial services is irrelevant to the UK, and that it's about tax sheltering. I think you've been reading one side of a political argument for a long time.
The financial services arm of the UK is the major moving force behind Brexit in the first place, they did that knowing full well that the rest of the country would suffer. It won't take forever for people to realize this.
And with multi-nationals such as Shell moving to the UK the balance is shifting further away from where it should be, now the UK will act as a de-facto tax shelter in all but name because it can afford to offer these companies great terms, after all, they have nothing to lose.
Depends on where the money ultimately comes from. e.g. it would be smart for Russia to fund leave.
No surprise they wanted to separate.
It is happening as we speak.