Hello! I was born in Bletchley, grew up in Leighton Buzzard and have also lived in MK but now live in South Northants so hopefully have a decent perspective.
Although I wouldn’t want to bring children up there (secondary school system isn’t great and places for the better ones are postcode based I believe, as is the gang violence), MK is a great place with a fantastic road system. However, prior to getting there, the same can’t be said of the roads that lead to it, so if DH needs to be in MK every working day, then just be mindful of that (specifically the M1 j15 south or j5 north as there always seems to be regular issues.
Personally, if I had your budget I would look at the following places;
Buckingham, Towcester, Woburn/Aspley Guise, Berkhamsted, Tring or Stony Stratford (and possibly Olney but don’t really know it that well) or most of the surrounding villages of these areas.
I would avoid LB, MK, Bedford, Aylesbury, Oxford, Bicester and Northampton too but that’s not to say there are plusses for these places and there are also some great villages surrounding them. Just journey to MK wise and personal preferences really.
From what you’ve said what you are after, I would go for Towcester/Silverstone area (particularly as traffic should be seriously reduced soon due to opening of a bypass) - ticks a lot of boxes and good transport links etc. No station though, but not affected by HS2 and Northampton, Wolverton, or MK stations close by. Plus my favourite watering hole is there so maybe biased based on this solely 🥴
Good luck with your search - I’m now off to pretend I’m you and put 900k in RightMove 😂