Re: I doubt she'll ever be Home Secretary, but...
As we are floating currency issuer, our spending is not determined by tax revenue.
When we bailed out the banks to the tune of several trillion, no-body knocked on your door and asked for a contribution.
What we spend our money on is a purely political choice, gated only the limit of real resources (bricks, skilled people, land) not sterling which is in itself a bet on the UK .gov honouring its issued gilts / bonds.
A bet, the UK has not failed to honour in 300 years.