I actually work in a day nursery in Sale so I would say Copper Beeches as it is fantastic and has especially great staff! M33 is surprisingly well served for nurseries, but you might find it hard to get a place for a 3 year old before they go to school. I know our waiting list is usually years rather than months, although you might get lucky with a 1 day place if you're flexible. Good luck!
mom101, I looked into Chestnuts, but it gets booked up very early. They only had 3 (specific, non-consecutive) days a week for a start in January 2014! So maybe check out their availability before you go any further.
Emmasonny, the prices are on the Chestnuts website.