Hi Rob ,
Yea , we have got ours , really easy , what we did was to arrange with our Spanish solicitor to go to the immigration place in Murcia , all we needed was copies of passports and both parents names , in all honesty it took us longer to drive to Murcia with her than it did to apply for the numbers , 5 mins , applications stamped we signed the papers and hey presto , job done .
I think you need a number for each person who is going to be named on the deeds....im not sure , if anybody could clarify .
Nothing to worry about , hope this helps.
Neil & Marg.