Looking for recommendations for an extender or mesh to extend Wi-Fi signal reliably in a 4 story Victorian terrace. Router is on second floor, Wi-Fi is fine on that floor & the floor below but poor on the 2 higher floors. I need to move my office to the top floor so need reliable Wi-Fi there. We are not tech savvy so need something that is simple to set up & budget for this is under or around £100. Wi-Fi is Virgin broadband.