Judging by the fact that the whois info for benalcars.com reveals not a lot more than the name Marc Chaplin, a PO box number in Newton Abbott and a UK mobile phone number, that the website is not working correctly, and the general 'feel' of this, I would guess that benalcars probably is no more...
The whois info does give an email address which may still be functional, that being mchaplin@telefonica.net. You could give that a try in your attempts to contact Mr Chaplin but I doubt you will have a lot of success.
If the car is legal and you have the sales receipt you can get replacement documentation from dgt.es and the ITV documentation from any ITV station.