"my old Almeria just ain't up to job of such a big drive down there with my trailer on the back"
I haven'y got a trailer (unfortunately) but I understand that it's not easy to get non Spanish trailers ITV'd (MOT'd) so you may have to consider buying one here.
Again, I'm not a builder but Vigas and blocks is a flooring system which would still need foundations.  Furthermore, I understand that they're not cheap and they're very heavy.  They would probably need craning into position.  Your most straightforward solution is probably to have pre-mixed concrete delivered assuming the wagon could access the site.