I've had it happen to me, in much the same situation as you Damien.
There isn't, unfortunately, alot that can be done about other drivers behaviour...
I just do as you do, and ignore it. The worst one I had was a cyclist... I overtook him (leaving about 10 feet between me and him) and at the next junction he was calling me all sorts of foul words...the only reason I could comprehend, was that he didn't like cars passing him...so rather random