Hi Dave-thorne,
Thank you for reaching out to us in our community and welcome, we are unable to send a longer cable however we can arrange for a technician to come out and relocate the Router, this is a callout and would cost a one off £25, this would go on the next bill after the visit.
So I can arrange this for you I will send you an invite into a private chat, once received please click on the purple envelope to accept.
As you have advised this is causing issues with WiFi, there are some great hints, tips and general WiFi support here including our Connect App, with this you can diagnose and fix most WiFi issues.
Regards
Paul.