Your speed test result looks a bit low (even if you don't get near to 1 Mbps, your test was almost half that)...did you close all other programs & only have your browser open while you did the test? If your speed tests are always giving around that result, you could ring TM Net & ask why you're seeing that speed.
That download speed of 539 kbps works out to 67 KB/s so with that result, about the best download speed you could get would be roughly 60 KB/s (LW shows your download speed in KB/s).

TM Net have a Fair Usage Policy, that's probably why you see slower download speeds. Click on the link below.
TM Net - Products & Services - Personal

Did you use Google to search? You'll find a bit of info about TM Net customers seeing slow download speeds.

You could try changing ports in LW, but there's no guarantee that it'll make a difference. In LW tools > options > advanced > firewall config. Change LW's listening port to 65000 (or you can try any ports in the range of 49152 - 65535) > apply > ok.

Do you see the firewall icon (brick wall in front of the blue globe) in LW? If so, you could try port forwarding for your Aztech. The instructions are here.
Port Forwarding for the Aztech DSL605EW
Don't forget to set up a static IP address first. LW's listening port, port number in the 'manual port forward' box & port forwarded within the router's setup should all be the same number. There's no guarantee that this'll speed up your downloads, though.

Also go through the thread about configuring LW, in my first post.