Something else that may help someone if they are thinking about whether they need to get a new router and happen to stumble on this thread...
With regard to my comment about the WiFi speeds being hopeless even right next to the router, I was assuming that devices with a 5GHz capable wireless network adapter would automatically switch to 5GHz when close to the router. This was not the case for any of our devices though. They were all connecting using 2.5GHz. Manual selection of 5GHz wireless mode in the wireless adapter settings on the devices doubled the WiFi speeds being obtained instantly.
Having 5GHz permanently selected in this way may not be any good if you want to connect to the router from a long distance like from the bottom of the garden but it works fine for us anywhere inside our house -speeds are pretty much the same as they are right next to the router in any room.
