Me : Sorry, not interested.
Caller: Don't you do any work for the public sector?
Me : Yes, I have, it was awful, I don't ever want to do it again.
I regret that I didn't add ' And there are better places for them to be spending than on pointless web projects*'.
* which is not to say that ALL public sector web projects are pointless, but on past experience, any that I am asked to quote for almost certainly will be.