I can't imagine such a thing would be particularly cheap. Surely it'd be easier to just turn the PC on and off remotely?
Why don't you just have Wake on Lan alongside VNC in your router if supported?
Maybe OP doesn't want to turn the PC off? Only mentions turning an extension lead on and off, which might or might not be for other devices..
If you feel like DIY then you can get something like this
http://www.ebay.co.uk/itm/USB-4-Cha...al_Components_Supplies_ET&hash=item4165b5b34b
and put it in line with the sockets.
As above, the PC is on 24/7 for my laser, and I plan on rigging up a webcam so I can see the laser and extractor / compressor and need to run a job when I am not there which takes 45 minutes. Means I can log in from home, and disable the extractor / compressor and laser.
Cheers. This will do perfectly fine. Good find! DIY is fine for me, I am playing with arduinoi, but I am nowhere near programming one for this. The one below is even better than I hoped for, since I can have everything on seperate channels (and stop stretching to reach the extension switches at the same time). The PC runs XP, so all is good!
Just watch out for the current draw as the relays are only rated for 10A on AC.