OP said:
"Budget would be £450k for a 4 bed detached house with parking. We'd be WFH so commuting isn't a factor.
When I say near, I just mean close enough for it not to be a big expedition to pop into Manchester for shopping or a night out.
Driving in is fine. Though public transport would be helpful for DC."
An hour by train from Sandbach is fine. Equally, out of rush hour in evenings by car its very doable. OP has said its an option worth considering.
Other people have suggested South Warrington, which the OP has said were an option. Now I challenge you to get by public transport to Manchester in an hour from South Warrington. Its impossible in evenings for a night out. An hour by train from Sandbach is much, much easier. By car from South Warrington it can take you 35 mins off peak but up to 1h 15mins in rush hour on an average day. Despite it being technically closer than Sandbach.
I have many friends / relatives in Trafford, East Cheshire and Warrington. I genuinely don't think its an unreasonable suggestion for any of these places because it reflects the lifestyles and commuting of people I know, who find that places closer in to Manchester are massively more expensive for the size of house / type of area they can afford with their budget.
I think the OPs biggest problem is actually her wish list and budget, because unless you look further out or towards less popular areas, she's just going to find it won't stretch far enough.
Personally, if she's not tied to schools, I think she'd be better looking towards the outskirts of Stockport and up into the hill on the South East of Manchester or the opposite side of the pennines on a good rail link, than many of the other places listed as I think she's priced out and public transport into Manchester that runs late is actually easier than a lot of places closer to Manchester because the networks are so poor. She doesn't need to commute regularly so reliability of public transport isn't a priority nor is the cost likely to be for an occasional trip.
FWIW, I think that Wirral and Chester is better for Liverpool than Manchester. But its not a million miles. I've friends who commuted from Manchester to Chester daily!
I guess it depends on what you are used to and what you consider 'normal'. I think my NW out of the city brain has different programming to city dwellers.