Hi there,
If you are thinking of buying a LHD Z3 here is a link to the Autoscout24 website for Spain where you can see what typical Z3´s go for. Remember, if they have been registered in Spain since new (not German imports) they should be rust free.
http://automoviles.autoscout24.es/?a...ge=1&event=pag
If you are thinking of buying a car and building it there you could have many problems and headaches with the I.T.V. (Spanish MOT) as the can be very fussy. Your best bet would be to build the car in the UK and then import it there fully finished. It would have to be LHD as I think its no longer legal to import and register RHD cars anymore.
Also the law says that if you are a resident in Spain you can only use a car for 3 months on its original number plate, after that it will have to be imported and pay local road tax. I suppose if you are popping in and out of the country "you might get away with it"
I hope this info is useful to you.
By the way, your GTO looks stunning :-)