Dealing with Unwanted Calls
Nuisance calls or texts where the number is known can be reported by texting 7726 see details on this OFCOM page
Calls should be reported even if the caller is on a withheld number (the number can be accessed by your phone provider). Notify your phone provider or call the police on 101.
Smartphones are capable of being put in do not disturb mode which can be easily configured with exceptions to only allow calls from your favorite contacts. Do not disturb mode can be set to automatically come on over night.
You can also set your phone to block withheld numbers.
These features are also available on some home phones eg Gigaset C430a
How to Block Phone Calls - iPhone
How to set do not disturb mode on: