ADSL2+ can theoretically provide download speeds up to a maximum of 20Mbps to eligible customers in selected areas and up to 8Mbps in many other areas but average speeds achieved will likely be lower.
Actual speeds that you achieve on an ADSL2+ service you will receive will vary due to a number of factors such as your distance from an exchange, the network connecting the exchange, your equipment and software and internet traffic.
Download speeds on devices connected via a Wi-Fi modem or network extender may be slower than on devices connected by Ethernet cable.