No- car test drives do not ask, its not a deposit as such but you sign to agree to pay up to £500/1000 IF you damage it, snap a mirror- you get your dosh back minus the cost of the mirror, its to cover the bike shops OWN excess that they have to pay on their insurance if you bin it.
Like I said before the shop pays the insurance excess (or rather you do) then the insurance pays out to the shop the cost of the shop fixing it - on which the shop makes a profit, we are not talking about write offs but just a drop will do £500/£1000 damage once you add labour cost, so you pay the shops excess and they make a profit on the repairs, sounds like a scam to me. Would not be supprised if the excess is much lower than tey say anyway.