Quite a lot of questions there!
I’d suggest you contact Graham Shelton at:
http://spanish-number-plates.comThe only way I know to avoid some of the import costs is if you are becomi g a resident and you import the vehicle as a personal possession. I think in this case you have to have owned it for 6 months and you have to do the re-registration within about a month of first going on the Padron. Graham will give you the details if it’s relevant to you.
You should also consider these two points:
1] rear fog lights may also need to be modified
2) UK insurance won’t normally cover you for more than 28 days when abroad, and not at all if you become resident in Spain.
Bottom line is that you’ll probably spend €750 - €1000 sorting out your car and when you’ve done it will probably be worth about the same amount if you try to sell it.
Driving a RHD car in Spain isn’t ideal for a variety of reasons, but you’ll need to decide if it’s worth the time, money and hassle to save buying at Spanish prices.
Pete.