apart from when a bolt is damaged and you need a slightly larger random size? lol i own no imperial bits
If you own an old British or American car then yes. They can also be handy as you've said for rounded bolts.
Metrinch sockets are the dogs wotsits. A single socket fits both a metric and various imperial sizes and is much less likely to damage the nut. http://www.metrinch-tools.com/website/introductie.php
I`ve got a load of Metrinch sockets that I bought in America a few years ago, and , they`re not all that IMO. The diagrams on the webite show them to be a good fit on a bolt/nut, but I`ve found there is actually a bit of slack on some sizes, that can cause rounding on tight fasteners.
To be fair I always find them when looking for any other socket I need. But combined with a hammer they're my best friend for the large selection of rounded nuts I seem to come across, sometimes invaluable doing what they shouldnt!
christ, you lot need to get some proper tools - using imperial sockets to to undo metrics that have rounded will result in them splitting, get some single hex versions, preferably in the impact variant, or look at getting a set of the below (Irwin bolt grips) http://www.irwin.co.uk/cdetail.php?cType=p®ion=uk&catCode=0&Cat=Bolt+Grip&crumb=