Not a stupid question at all. In the current climate, everything is negotiable when it comes to property. All they can do is say no. A lot will depend on the financial position and attitude of the vendor. You can't know that until you test it.
If I was going to bid below asking price, I'd make myself as attractive a purchaser as possible. So before making the bid, I'd get mortgage approval arranged for the property so that you can assure the purchaser that if s/he takes your offer, s/he can have their money in a very short period of time.