My old instructor was like that, went 10 mph over the limit once (because i never look at the speedo and didnt realise he had a 1.8) and breaked to about 10 mph then started screaming at me. I got rid of him and my test was 3 months away so he lot about 100 quid lol.
I think it is the older instructors that are a bit **** actually, cause older people just get more stressed easily and if hey've been driving with people that can't drive for 40 years plus, it must really piss you off. I bet they almost die every day actually, cuase there are some propper retard learners. anyway driving 2/3 of instructors I had were complete *****