sagemcom 2704n woes

[#1]

Just come over from bt fibre up to 40mbps and was getting high 30's wireless, on my main pc down the hall from the master socket. Master socket and modem/router are by the front door but there is a brick wall between PC and router. Same PC with sagemcom 2704n router I'm getting -25Mbps. Got hard flooring in hall and my den. Hard wired to the router my laptop is getting 74Mbps. The sagemcom 2704n is obviously a pile of poop (cant even connect my samsung s6 upstair reliably). What are my best(and cheapest) options to get a good wifi connection. I still have a BT home hub 3 available.
Regards

[#2]

You can still use your HH3: http://community.plus.net/forum/index.php/topic,135840.0.html

[#3]

Managed to get BT HH 3 going. Was getting same speed initially, but after a few tests I was getting 45Mbps. Then it's dropped down to 32Mbps and stayed there. (Lower than it was on BT up to 40) I'll have to find my usb wireless dongle extension wire and see if that will help as my PC is on the floor in the corner of two brick walls. Strange it should be slower than my original setup as no equipment has changed location.
Regards

[#4]

Found my usb wireless dongle extension wire, so now the dongle is two foot higher sat on my desk. Made the world of difference. Now getting 70Mbps. Now I'm a happy bunny.