Thanks to all of you for your replies, some intresting and thought provoking stuff.. Our clause re £100.00 item is already covered within english insurance laws i.e. unspecified items lost away from home such as gold bracelet. If its not on your policy as being worth say, £1500.00 and it gets lost, as far as most insurers are concerned they will limit the value to £1000.00.
Our clause is not to 'shirk' true responsibility but merely to cover the 'vase from Woolworth's suddenly becoming a family heirloom after it hits the floor!!!' ,, and yes this is intended for houshold sparkles.
Our solicitors have stated to us verbally that we are entitled to use this clause as long as it is written into the formal quotation and with a written acceptance of it by the client would hold in court, subject to, of course, the level of 'negligence on the part of the contractor to take steps to protect the clients interest' So yes I agree that this is not an iron clad protection but it does draw the client's attention to items that perhaps might be better moved to a place of safety by them prior to the clean.