I think the UK needs to consider some serious downsizing.
We should let Shetland and Orkney secede, taking the UK's rights to the North Sea oil with them. That will show Scotland. They can then join Norway, reviving historical links and getting access to the infrastructure needed to manage that oil.
We should give Gibraltar to Morocco, who can swap it to Spain for Ceuta and Melilla. Alternatively, we could give it to North Korea, just so we can watch the Spanish Google "Nodong missile range".
Northern Ireland should of course become part of the Republic. In order to prevent Protestants being too small a minority, they can take Glasgow along with them.
The Isle of Sheppey can be given to the Netherlands, to commemorate the Raid on the Medway.
London already is Singapore, to a good first approximation, so the fastest way for the UK to become a modern city state is to evict the rest of England and Wales and Scotland, leaving Westminster governing greater London. That should also end any calls for further devolution. Until Highgate decides it wants to go it alone.