well it seems to me the CPU has slow down, maybe after a reboot is better, maybe if you disable the wan is not in use may helps, maybe the power supply getting old, maybe some settings prevent the speed such firewall or dos or QoS (that can slow down the speed as well or bandwidth management) have you disable them?
Maybe a firmware update can help (latest is 3.3.7.5 but note it needs special care if updating from 3.3.5 can cause issues if not update correctly - check the release notes)
Sorry i don't mean in bad way because i did tried some small suggestions but as mentioned the unit is build for 50 mbps, anything more than that,t i can not blame it really if has slowed down after 2 years of use

Thanks for your reply.
I have done most things i could think of.
The firmware has been updated, new power supply. All the QoS settings are off, only the 1 wan port is enabled.
Rebooted so many times.

After reading your comments about the speed limit i did a few other tests. It seems if i down power the router for 10 minutes, Power it back on and do a speed test straight away i get around 73 ish, but then the speed seems to creep back down again slowly so I'm guessing the CPU cannot deal with it.

What other Draytek router would support what i need without problems.

Thanks

i am not sure but it could be because running for 2 years to its limit can make tired the CPU
It is worth to check the power supply as well, if you have one with similar volt & amber to try ( if you can get the amber little higher it helps to run the unit smoother ... for example if the PSU of the 2820 is 12 V - 1,5 A get 12V of course but 2 A

The latest & closest to the one you have right now of the range is the 2860 it can go up to 200mbps, so you understand should run without pressure (at its limit) for long time ... it has build adsl/vdsl modem and second wan, same design box & color& also same menu as the 2820
http://www.draytek.co.uk/products/business/vigor-2860

i am not winning commission from the shop but if you want a bargain look left grey tab "buy used item" for 133£ right now ... if it has issues will show them from the begin & the shop get returns & warranty for used item 90 days if there is a bad case ... so don't worry
http://www.dabs.com/products/draytek-vigor-2860n-adsl-vdsl-wireless-router-8W2G.html?refs=4294963788&src=3

But first check the PSU of the 2820 if has issue with an other one

babis3g wrote:
i am not winning commission from the shop but if you want a bargain look left grey tab "buy used item" for 133£ right now ... if it has issues will show them from the begin & the shop get returns & warranty for used item 90 days if there is a bad case ... so don't worry
http://www.dabs.com/products/draytek-vigor-2860n-adsl-vdsl-wireless-router-8W2G.html?refs=4294963788&src=3

Good spot. That is a very good deal £133.00..