To be honest, that's not a great deal of money for a house for a London commuter, and you are going to have to make compromises (as I'm sure you realised pretty quickly). I'd guess that your husband is going to have a pretty awful commute, or that you'll have to drop the idea of a character property.
Frankly, if I was commuting to the station every day, Hist/Imp would be one of the last places I'd want to live. How on earth is your husband going to get to the station? As Kickassangel says, it's 30 mins to the town centre itself, and congestion charging may well be coming in before too long. Please don't buy a house to the north of Cambridge before actually doing a test drive / cycle / bus ride at the time that he'd be communting. The new guided bus route goes via Histon, but I don't think it would be practical to get to the station - it's geared up to take people to the science park and then the centre, if I remember right.
I wouldn't exactly call Histon a bustling metropolis (or even very pretty, to be honest), but it does have enough shops to save you going into town, and there's the football team .
Impington VC has a very good reputation, but a friend who used to teach there didn't particularly like it (he left a year ago). I could never put my finger on exactly why, but I think that he didn't really feel it lived up to its aspirations / way it presented itself.
Waterbeach sounds logical for the commute, because of the station. I'm told the primary school is lovely - a friend volunteers there. I've never heard my friends who live their complain about the army barracks - but I don't know how lively it is. I can't imagine it's any less lively than Histon.
Moving from London, and commuting into London, I'd be looking to live someone within cycling distance of the station and Mill Road. Something more like this
www1.housescape.org.uk/cgi-bin/full.pl?&vin1&&VIN1000736 (for size)
or this
details.vebra.com/property/671/17638415 (for character)
You might like Barton and Comberton - very good schools, and you get to go to Burwash Manor with the kids and shop while they look at lambs. Barton's also very pretty. 30 mins cycle to the station, or 10 mins in car not at rush hour. Burwash Manor is more fun for shopping than Histon, if slightly less practical, and at least there's a cafe. The pubs in Histon are much better, though.
This house might not look terribly exciting, but it might not be a bad bet, and with that huge garden there's loads of room to extend and you'd certainly have the budget for it:
www.homesonview.co.uk/Scripts/ShowProperty.asp?css=&CompanyID=REDMCAMB&AgencyID=REDMCA MB&ID=RCP00164
Hope that's helpful!