Why are you keeping it indoors? Have you ever heard of anyone having success with one inside? I am not sure you could grow one as a houseplant...I can't imagine any plant that needs to be watered everyday inside. You can plant blueberries in the fall, outside if that is possible for you...Good luck!
Not to worry- the leaves turn reddish as fall approaches. I planted 50 green bushes in spring. All have survived and all have a reddish cast to the leave. Your English weather couldn't have been wetter that ours! Record number of rainy days in June and July! I think summer is finally here, this week! Good luck!
I live in England but I have never bought them inside & they pull through our winters without any problems -- even the last one....!!
May I suggest that you add a clue to our friends here in TEG as to where you live (as I do) -- you don't have to be too specific. It makes It easier for them to give advice & also makes things more interesting!