Thank you for that information.
If your handset downstairs is a cordless phone then you would simply be able to plug in and use.
For a corded handset, we would need to send out an engineer to fit an extension that will require additional wiring. There would be a cost implication to this of £25 though.
Please let me know if you wish to proceed down that route.
Thanks for taking the time to work with me over our private messaging function @bri201, and I'm pleased we're able to take steps towards getting this sorted out for you.
Do feel free to come back to me via our private messaging conversation if any issues are encountered and I'll be on hand to assist where possible.