Linux
Still don't see why the UK government don't look into it more.
I mean, a lot of what government offices do revolves around very few things
email / word processing / database.
Email and word processing can easily be done on a linux system, and database the difficulty would be finding replacement software. We aren't stuck at the same point we were 15 years ago where you had a choice of microsoft or a command line with no useful applications for the general user. the majority of software you use on windows can be found in some freeware out there.
By the time you work it out first year or two of changeover costs more what with admin fees installing and setting up everything, and retraining staff to use the new software. But after that initial bumpy bit on the road the price drops immediately.
Heck they could even test the system out at some smaller distric councels