Cranberry plant help

Hi I bought a cranberry plant last year reduced. It looks ok however it was pot bound so i repotted it. But then it got attacked by fungus gnats which i have almost got rid of all of them. It still looks a bit sick and it drops a fair few leaves sometimes. Any advice on how to get it healthier and ready for planting out this year? Also when is the best time to plant it outside in a big pot? Plus what is the best way to get it used to the cold weather?
Any tips or advice will be appreciated

 

Hi Wardy have a look at a site called cranberry creations, sorry can't post a link on tablet, don't know how.
Seemed informative.

 

I'm sure I've read somewhere Wardy they prefer to be in open ground and preferably acid soil but check up first there's every chance I've got that wrong

 

Yep, don't water with tap water if you live in a hard water area

 

Thanks