Scotland and Norn Irn have voted heavily in favour of nationalism, which is a big concern. We could see the break up of the UK in the near future if things aren't handled carefully.
Well if they want to leave, and think they have enough tax payers to support them, then let them go, as that means all English tax collections stay in England, if you talk to people with a bit of education, they all stay that the amounts Scotland would make from oil and whiskey, isn't as much as WEE Jimmy thinks, and Ireland would struggle to.
On purely financial terms your right. Historically when the heavy industry was still around, the North of England, Scotland, Wales and Norn Irn more than paid their way within the UK. But those days are gone and aren't coming back.
Despite what anyone wants to believe, Scotland and the rest of the UK 50 miles outside of London, is heavily subsidised by Southern English taxpayers, and would flounder without that subsidy.
Theres more to it than just financial considerations though. The UK has been an incredibly successful political union for centuries, whether in warfare, industry, the arts, culture etc. etc. and I believe all concerned will rue the day if it is ever broken up.
The UK has punched above its weight for a very long time in almost every measurable way.
It might be a clever move from Boris to flood Scotland with more cash for two or three years, then give them another referendum, hopefully win it, and shoot Wee Jimmys fox in the process.