A couple of points to note. No matter how slow your router is in teh scheme of things, it'll be a damn sight faster than your broadband line unless you're over a dodgy wireless link too.
0.5 meg line is quite honestly shocking. You could bearly get streaming decent quality audio at that rate, let alone video. You need to have it saving/buffering.
However I would see if it's any better at other times of the day, i.e. 3am. If it is I'd suggest your ISP may be either overcrowded on your local exchange and/or traffic shaping – i.e. limiting certain types of traffic to prioritise others. Tiscali almost completely block torrents at any time of the day, but if I tunnel them through an SSH connection to my parents BT address I get fairly respectable speeds.