I live in South Wales and have been having issues with intermittent IMAP connectivity. This is with email clients on my MAC, PC. The issue is also evident on phones and iPAD.
I have discovered that the problem all but disappears if I enable my VPN, suggesting to me that there might be a problem with the Virginmedia network locally.
This problem is evident on my ntlworld and virginmedia email accounts. I don't have the same problem with my gmail account.
I haven't contacted Virginmedia yet as I would like to know how many other people are experiencing similar problems.