I think you need to avoid making a hurried decsion if you don't know the areas well. It can be hard to gauge an area from visiting it and far better to try a place out at different times of the day etc, which I realise is an almost impossible task in your position.
I'm going to stick a fly in the ointment and say I wouldn't move towards Northwich/Hartford/Sandiway - sorry - I've just never warmed to that area, which is a shame because we could afford a much bigger house there - which is perhaps what's attracting you at the moment.
Do you have a property to sell? Can you come up and rent for a while?
I live in Cheshire and I know it well. Depends what you are looking for and how much you want it to mirror your life in Surrey.
In your position (and with your budget) I would be looking at Holmes Chapel and South Warrington. I must admit we have considered living in Knutsford ourselves and I agree with you that it's overpriced. In truth, the high school has a poor reputation too - good primaries but many of the kids are creamed off for private school. For us, the high school was a deal breaker.
Holmes Chapel has a high school - have you looked there - I think the schools are ok? The prices are much more reasonable.
South Warrington is ideally placed for the motorway network and you could reach Knutsford in about 20/30 minutes. The high school is called "Bridgewater" and it gets the best results in the town at GCSE. There's some lovely countryside on the edges there.
Wilmslow is pricey but lovely - you have to be careful around Handforth though - cheaper prices but not nearly as nice - and the high school is verging on similar to Knutsford.
Rightmove around "Appleton" or "Grappenhall" in Warrington and Holmes Chapel and Wilmslow and come back and we'll be able to advise you better!