I've browsed many reviews and have yet to find one that does not rate this as good to excellent.
I saw it myself tonight in a sold out theatre. Laughed, cried, cringed and finally emerged changed and thoroughly satisfied. A moving, British-based political drama of one who dares to change his world by living what he believes and working faithfully within the system to reach his goal.
I would see it again in a minute and will buy it as soon as it is available in DVD. A classic.
Go. Watch. Enjoy.