water damage

It will be somewhat dependent on what country you are located in, but here is the information from the US site.

Have AppleCare+?

AppleCare+ covers two incidents of accidental damage each with a $79 service fee. You can also use our Express Replacement Service to get a replacement even before sending us your iPhone. You can check if you have AppleCare+ by entering your iPhone serial number.

Out-of-warranty* cost:

Make an appointment at your nearest Apple store to take the iPhone

in for evaluation.

If you go to the Apple Support site for the iPhone, you will see a section where you can click on for Repair and Service, and you should see a link for Other Repairs and you should see a table with UK prices.

Should be. That is the out of warranty replacement fee. Apple would not charge you anything else, unless you have to pay tax or something like we do here in the States.

You're welcome.