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I've got the same feelings. Wi-Fi signal is not very good on 1st floor...getting disconnected constantly and download speed is really bad. I'm new to Vodafone. I wonder if I can connect Wi-Fi extender via Ethernet cable and that will give me more reliable connection to my pc. When I'm on ground floor where the router is, experience is not as bad.
that's what I did, I got a pair of TPLink , but be aware that this solution has some minus, I have issues with those TPLink some disconnects (sporadic issue , as there are times without an iterrupt,) and I read a lot of people have this issue , not only with the TPLink btw, it depends of your home's cabling btw., but anyway it was the only solution to connect my PC on the net, as the rest of the family had no signal downstairs (mainly for the Roku on TV)
Vodafone now supply usrname and password on request, I got mine on chat last night, you just have to pick an authorised router from the list approved by openreach, you dont have to buy it, just mention it