Update:
Last night I switched my DSL modem cables from the Computer Dynamics 5m RJ12 to 2m RJ12 version. This straight away gave me a speed boost of around 5Mbps. I attribute this to the fact I had wrapped up the extra length and this may have caused some inductance.
My Draytek DV2765 arrived today and I wasted no time in setting it up and testing it. I am pleased to announce the speed gain going from G.993.2 (Earlier models DV130, DV2762) is real. This gave me a further 13Mbps on top of last night's gain.
This is not quite as much as the Fritzbox (Speed Test around 93Mbps) but there is nothing about that product which could persuade me to use it for the extra 7Mbps. Additionally, its possible all the "testing" may have knocked me back a bit.
In summary I have gone from a respectable 68Mbps to an even better 86Mbps.


