Just to be clear… which UK ticket are you buying?
I’m not sure if the terms have changed but historically they have worked like this:
There is generally 2 options. One is a 7 day hopper, the other a 14 day hopper.
The 14 day ticket would get 14 days of theme park admission usable over an 18 window, PLUS 14 credits to access waterparks or golf. Those credits could be used at any time over that 18 day window.
You could overlap with a theme park day or use on one of your days off. You could even use 2 of those credits (entitlements) the same day, like going to the waterpark from 10am-3pm followed by a round of mini-golf. You could even overlap those credits on one of your park days, like hit Hollywood Studios in the morning, go to Blizzard Beach in the afternoon, then hit Magic Kingdom that night.
The 7 Day ticket worked in similar fashion. Got a 14 day window to be used, with 7 days of park hopping PLUS 7 entitlements/credits to be used at waterpark, golf, minigolf, ESPN on any of those 14 days.
Unless things have changed, if you buy a 14 day hopper you should have plenty of waterpark visits included. More than enough!