The higher speeds VDSL (fibre broadband) delivers are more susceptible to home wiring issues than ADSL or 'ordinary' broadband if you like. Specifically whats called 'star wiring' where the line from the exchange is not connected directly to the main socket first and then out to the extensions, rather it terminates in a multi point connection with wires out to all sockets. Also old obsolete main sockets can affect speeds and stability. Usually you can ask for a full install where any of these wiring issues will be sorted even if rewiring/resiting of the main socket is required. A VDSL specific filtered front plate is then usually fitted to the main socket to filter out all the extension wiring. If you're paying for a faster fibre connection it seems daft not to get the wiring sorted and make the best of it.
As far as cordless phones go we've had a Panasonic (1 base station, 3 handsets) for a few years now and apart from replacing the rechargeable batteries it's been faultless and the range is very good, even with the base unit downstairs. As with any RF device, the higher you site the base station the better.
