the pumps are 12 volt submersible bilge pumps, and cost around £12 each, and the other end of the circuit is controlled by a couple of fluid level switches at a fiver each. but as the switches are only reed switches, and can only handle a max of 1 amp, i'm using them to switch a relay which can handle the 5 amps that the pumps draw.
the pumps are supposed to push a 10m head, which, for the price, i thought was pretty good, in practice, probably because of the convoluted pipework to the upstairs loo, it doesn't exactly gush out, but is sufficient and thats an estimated 5m head. I'm really pleased with the way it all works, If i can cure the pong it'll be a complete success. I have drained the tank and cleaned it with anti-bacterial spray, also bleached the shower/bath waste pipe, so the next few days will tell me if a constant cycling of the sump keeps it sweet, if not then it's going to be some form of aeriation as plan B