It annoys me when people print or tell you their telephone number as 0207 xxx xxxx. For some reason I find it harder to remember 4,3,4 format than 3,4,4 (no doubt someone with psychiatry knowledge will explain why this is and take us even further off-topic!).
The Coventry area went from (0203) xxxxxx to (01203) xxxxxx to (024) 76xx xxxx, but look at the typical Coventry small business and it will be printed as 02476 xxxxxx.
I wonder what proportion of calls to landlines are dialed using the local number these days, particularly given the proliferation of mobiles.