Do people still seriously rely on dialling codes to identify areas?
Speaking personally, if I want a local plumber and all I've got to go on is the number on the side of the van I saw parked outside next door, I'd call someone with a local (or neighbouring) area code before I called anyone with just a mobile number. Not seen this kind of sole- or small-trader use non-geographic codes; they cost real money for very little benefit unless you genuinely are a national company.
As for my place of work, it genuinely does confuse people. If a teacher at a local school wants to talk to an education officer at their local museum and is given a direct-dial number which appears to be for a site 150 miles away, they're going to wonder if the person they are speaking to is the person they really need to speak to. I don't deal with teachers, but I do occasionally have suppliers ask "can I just check I've called the right number?"
Yes, we do have a non-geographic too. 0300 as it happens, but you can't do direct-dial on this one.