[Nissan Juke 2015 Radio cutting out and Touchscreen not working]

These issues sound a lot like software problems of the actually audio unit. Nissan do run software updates but you have to visit a dealer and request it. The update usually fixes issues such as Bluetooth connectivity issues, calibration and restarting issues. If problems persist however then you’re looking at audio unit replacement which I think are fixed in France. 

[Do I need to change water pump?]

You should ideally change both at same time given they’re both the same age and done the same mileage. 

[Climate control]

Common fault on Qashqai is condenser failure. Perhaps your A/C system doesn’t have gas in and isn’t working accurately. 

[Fuel Pump Regulator problem - won’t start.]

Hi,

what codes showed up when you had it checked?

I’m sure you can’t just purchase the regulator as it is inbuilt into the fuel pump on the 1.5 k9k engine so you would have to fork out for the lot