I'm going in mid Aug. Have read mixed reviews on Trip Advisor so am just trying one of their Sunset Evenings which are a lot cheaper than a full day. A friend rented a flat in the mill complex and it was a bit run-down in terms of landscaping and a bit un-finished, but when I went into the reception area of the spa itself to get a leaflet, it seemed ok. If you're W Yorks based, I've been here before - was very reasonable, but small. http://www.waterfallspa.co.uk/spaleeds.php
I have and it's gorgeous! Food is out of this world and treatments fab but a bit pricey (although depends on if you want treatments or are happy lounging by pool and in sauna etc). Agree about the rooms - although I didn't think they were particularly run down, rather I think they were trying to go for 'rustic' look IYSWIM. Not to everyones taste I suppose but there again how much time would you actually be spending in them?