mate it doesn't really matter what you go for you could get a lurcher/lurcher cross and not really know what's in the mix and it could be better than the crosses mentioned but to put a cross on paper I would go for whippet x collie/grey. 1/2 whippet 1/4 collie 1/4 grey, good for mouching and lamping, good feet, brains, speed and should turn good to also calm and relaxed like you wanted but its up to you and im sure no matter what you get you will be happy with it. atb