Finding this a bit of an odd thread really. Where exactly is 'out of London'. Everyone's experiences will be different, depending on where they have moved to and what sort of person/family they are.
Does your husband have to work in London or could he change jobs? One night away a week sounds manageable, although not desirable, any more than that and I wouldn't like it one bit.
What sort of things do you like about London at the moment, and could you find those things elsewhere or be prepared to visit London often enough for them?
If you need to be within commuting distance of London, find yourself a radius where this would work and look at the places to live within this radius. You don't have to be very rural and all 'fresh air and glowing cheeks'. You can be small town, larger town, small village, totally out in the sticks and many variations on these themes.
If you like sport, shopping, theatre, museums, bars etc, find a town with easy access to them - I've never yet lived anywhere I couldn't access these things fairly easily. That's because I know what sort of person I am - hate living in a city but wouldn't do really rural, I need to be within walking distance of the sorts of things I do day-to-day, and to have other things within reach. I live in a small town with everything for everyday family life as well as being only 15 mins by train from one very cultural city and 30 mins away from another very vibrant city. Perfect balance for us.
I have always loved London for day trips and weekend stays, but hated it the short time I actually lived there. We still 'do' London as a family from time to time but there is nothing London has to offer that would tempt me to live there, most things really do exist outside London. If you really feel differently and can't imagine life outside London then perhaps moving isn't for you.