Bought hundreds of Lowara sub pumps, these DOC pumps work well with grey water with very few failures providing the run dry is wired right.
Linked to a couple of high/low MS10B from RS they will give years of service, I might even have some left over and I'll check when I'm back in the office.
I've also issued these cheap bilge pumps to all our tech's for pumping out meter chambers, cheap and cheerful with a decent flow, I just wire them to a cigarette lighter plug and connect to some 22mm (iirc) hose,
These do fail but we've had a few years out of them being used for say a couple of hours per week.