You can't and they won't be that fresh...
The councils that abide Uber regulate them the same as any other driver. When I was taxi driving, I had my own operators licence and car but wasn't able to sign on with Uber as I neither were London PCO registered... Phone numbers can be mobile, but address must physically be in Greater London for that to happen... Which wasn't going to happen 
Driver vetting is pretty much standardised now: Medical, DSA advanced test, CRB check and some sort of test of understanding of private hire licencing conditions. Uber in the UK should be no different to any other firm operating...
the drivers in & around York, Leeds, Bradford & even further afield do flit from town to town. I have often wondered how they are allowed to. if I wanted to start taxiing in York I would need to pass a rigorous knowledge test.
There is a little loophole in the law, that they maybe using.....and that is..
If you have a vehicle and personal license as a hackney driver......you can legally work for any private hire firm in the country.

However it could be also that local authority licensing them as hackney drivers covers different towns, so this would also be possible.
What is not allowed by private hire firms is that a customer phones say a private hire in one town/city and that company then passes the work onto a firm in a different licensing authority area....
Regarding knowledge tests....I never had to take one, as I had my private hire license before they were introduced into Swindon.....but in Swindon they are a bit of a joke tbh. Iirc hackey driver get asked more questions than private hire drivers....the reasoning behind this according to the council, is that the private hire drivers can look up their destination before picking up their customer....So...my company uses a system called IVR....the customer never speaks to anyone and just orders a cab from their location by pressing buttons on their phone, whether its from mobile or landline....on my screen the destination comes up as "as directed" . Also my company uses a phone app, if the customer carnt be arrised to input the destination, again on my screen, it says "as directed" ..... so not much different to hackney drivers really

Regarding Uber....Uber have blanket applied for operators licenses in just about every licensing authority in the UK....and got them...whether thy use them or not is upto Uber....
And theres no way private hire drivers can switch between different licensing authorities unless they actually move to different authority area......unless they fraudulently apply for their license ...