Just seen this thread when searching something about Hulme Grammar School. Probably too late but just in case it is ever useful as I want to share our positive experience:
After an awful experience with a local school, we use Hulme Grammar (prep) in Oldham for two children. We find it to be a really excellent school and are just disappointed that we didn't know it existed sooner (we had never considered Oldham as a place for a school). Our eldest (who has dyslexia) gets fantastic support and encouragement which is helped by the small classes. They are thriving there which is great as it was not nice to put them through a school move in 2024.
We are from south Tameside so many people here use Stockport Grammar but that would be too far from Saddleworth. However, compared to SGS, Hulme has similar results and is much easier to travel to. When looking around, we liked how Hulme talked only about our children and what the school would do for them, not about the school. That was a clear difference to the other places we looked at.
Lots of people from Saddleworth go to Hulme so if you have chosen it, your child won't be alone in the area.
It has lots of extra-curricular opportunities that you would expect of any private school and the prep school has specialist subject teachers etc. The school is very receptive to feedback and you can have proper adult conversations with staff (there is no defensiveness unlike our previous school). Whilst I know it is a selective school with high standards, it doesn't have a "elitist" feeling which is what put me off private schooling until we went there. I understand that some people chose a private school for that elitism though.
Mindful that this sounds like an advert I should stop...
MGS is obviously an excellent school with better results than Hulme (but you never know how much of that comes being more selective vs. how much is from better teaching) but you also hear stories about how competitive and pressured it is - I didn't want our children in that situation. I wanted them to be in a good school where they could achieve their best, not necessarily one that pushes pushes pushes. I also would not want to do Saddleworth to MGS on a daily basis, but I guess some people don't mind that.
You don't have lots of other options from Saddleworth, perhaps Bury Grammar School which hasn't been mentioned above. Good luck with whatever option you selected.