pls wrote:

Incidently, does the conduit have to be steel lined (its going to be
buried mostly under a patio) or can it just be standard flexible PVC
conduit?
The steel lined one I've found is he
http://cgi.ebay.co.uk/30m-Length-of-...QQcmdZViewItem

Ah, flexible conduit and an underground application - two things you
hadn't mentioned before. What is it you're trying to do?

You shouldn't use flexible conduit underground unless it's a type
specifically designed for such use. Nor is it very sensible to be using
single conduit wire underground. Better to use SWA cable, which can
be buried directly, or a sheathed cable such as ordinary T&E or Hi-Tuf
in substantial plastic service duct.

--
Andy