Good luck dividing England up into such states!Germany has 16 states with a population about 20% larger than UK. US states have an average population of just under 7 million. 7-9 English States + Scotland, Wales and Northern Ireland would be directly comparable. 5-7 million is an optimal level for good governance, states and countries that size do tend to be well run.
Fixing a border for London would be a huge issue if it actually made a difference.
There is a really big reason not to divide up the UK - it would hugely emphasise how London particularly, plus the South East and East Anglia, fund the rest of England. Cue much bitterness, and calls for London to pay less federal tax, or get more spent on it (and the attached GERS type arguments about how on Earth you split revenue and taxation to decide what the net figures are anyway)