My first Wherry, whilst eminently drinkable, was also a bit watery, and I'd followed the kit instructions to the letter. If you used the measurements on the side of the brew bucket (like I did), they are not that reliable and that could lead to over-dilution of the wort, so for the next brew, try using a more exact measuring method. Saracen's well-regarded Wherry tweak uses less water and is designed to give a much fuller-flavoured Wherry (still waiting for my tweaked Wherry to condition, having had a leaking seal on the keg).
Planning: Golden Stag Summer Ale
Drinking: Tweaked Wherry