Certainly on daft there is a tickbox to choose Female Only, Male Only, Either Gender when placing an ad looking for people to share your house. When this appears on the ad though it's says something like Female Preferred - I think you're allowed state a preference but can't outright say you won't take anyone. Mind you, you'll see a lot of the ads saying non-smoking professional females only. It's one thing to not discriminate against a tenant when all you really should be looking for is someone to keep the place tidy and pay rent and bills on time. However, when you're looking for someone to share a house with you there's a lot more to take into consideration - I wonder how the legislation takes that into account.