My room was on the ground floor room and wasn't dark or dingey, I think what you mean is that the rooms on the lower ground floors are right into the gardens, there is nothing dark or dingey about the Turquoise although obviously i haven't seen all their rooms lol. Look on the 'bright side' at least the rooms will be cool if they are dark and quite honestly, if you were to find them not to your liking, they are SO very accomodating there that I'm sure you'd be moved if you felt that strongly.
Can't fault the place, been there twice this year and love it.
(Highly recommend their Turkish bath as well, get the full works, complete body massage after as well, all for 25 quid, fantastic!)