You are correct. A quick search confirms that there isn't such an area code. Many scammers use internet based calling systems that can generate random numbers that seem real but actually aren't; unfortunately Virgin can't block them all. There have been other posters that have had the same problem where the scammers have been a bit more organised with their numbers using valid area codes. However, a simple internet search would at least give these guys a more believable number.
Thanks for getting back. I've had five of these today. One on the hour and the same last Friday. All different numbers. If I was a vulnerable customer I would find this quite upsetting.
If ALL the landline providers could provide a means to block these numbers or area codes it would be great. You can do this on your mobile phone but handsets aren't so clever. I am sure they have the means to provide this on-line; they just don't.
My guess would be that electronic call blockers/phones wouldn't block the numbers as they aren't valid, particularly in this case. It's the same with caller recognition systems. I've had calls from 0000000 on the 1471 number recall along with several spoofed numbers that are also from "valid" area codes. Spam calls and emails are, unfortunately part of modern life.