I did, I got a veteran's discount. When I was there the dealer told me the dealership makes about $600 off each micra they push out so that's the headroom they have to play with before the profit turns into a loss. Keep in mind, thats a micra 's' and not the upscale model you've picked, I would assume there would be a greater amount to play with.
If I remember right, and from what my grandfather tells me (long time london resident) most of the dealers in london are in a group and basically work out of the same wallet, so wither or not you go to dale downey on oxford st, or south london on wharncliffe, they aren't going to care because its all the same pot.
If the etching is on the car already, then yes, they will want to make the money back from what they made and it seems that the actual cost of said etching is a closely guarded secret.
Ultimately its your money. So if your not getting what you want, then I would contact another dealership outside of the london area.. For example toronto, belleville.
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View my fuel log 2015 Micra S automatic: 7.9 L/100 km ... 35.7 mpg (Imp) ... 12.6 km/L ... 29.7 mpg (US) ...