I'd ask the dealer about the key as I'm not sure. I've always bought aftermarket rubber mats and never had a problem. Boot wise, there's lots of different options such as hard boot trays, rubber boot liners, plastic stile ones that cover the sides/backs of seats etc. Not sure about the scuttle, but I'd recommend going back to the dealer and having a look at similar ones on the forecourt to see if they're the same. Interior lights shouldn't be a problem, if you were to change reverse lights to led as an example then this would throw up a bulb out warning unless you were to get error free ones. But as I say interior ones should be fine. I'd get it back in for the mirror to be looked at as there shouldn't be a difference between them.