Righeo, my take on things...
Do it. You can always go back to IT if all fails.
I'm in pretty much the same situation. 4 years of Uni has resulted in a series of contracts for government organisations and then 2 years employed as a IT Researcher for a Local IT firm.
I've done commuting. I've done government - central & local. I've worked for ******* companies. I've worked for good companies. I've done jobs for the money and not the happiness. Each looked good from the outside, but all had drawbacks each and everytime.
I basically got completely disenchanted with the whole shbang. But, with the wife doing an MSc, her tied into a lease car scheme, and us trying to build a temporary house (Log Cabin) (plus associated loans!) and save for a mortgage - I couldn't afford to even look elsewhere!
However, the time came when I realised I needed to get out as it was doing my mental state no go! Progressively becoming more depressed and all that it entails, we decided that, perhaps, we could do without the cash for a while!
Within 3 weeks of making the decision, I was offered a post as a Youth Worker. Not an entire career change, since it's something I've been doing on a voluntary basis for the last few years - but it now needs to support us financially! And, from what I've seen and heard, it looks very positive. Fingers crossed - I start a week Monday!