Please note: All of the below are only qualified guesses, as I am not familiar with the Spanish electric system.
> any more help would be greatly appreciated
I'm not sure of the purpose of your questions. Do you intend to rewire the house or just want to make sure that the wiring is safe? I don't think we can help you with the former and only maybe with the latter.
> our house was built in the late 70s at a guess.
That is not very old, in my humble opinion. The wiring should be just as good (or bad) as it was when new. (Plastic cables age very slowly)
> there is a dedicated feed to cooker.
Is the cooker gas or electric? If electric, I'd expect it to be 25A single phase.
> what seems to be 1 earth type skt in each room and to rest of skts are only 2 pin and
Two round pins with side earth? (Commonly called "Schuko" sockets)
> yes its all run in flexable conduit with singles.
Good, because if the wiring is in conduit, you can add an earth wire to the existing wiring.
Although possible, I doubt there are different circuits for the sockets with and without earth. There is a fair chance they have just pulled to earth to one socket per room, and continued neutral and live to the other sockets. This makes it even easier to earth the remaining sockets.
You should be able to replace the singles with doubles if you want to. "Semi-flush" double sockets fit into single boxes.
>most but not all of the light switches have a fuse along side the
>switch to step down to what seems to be any thing from 2 to 5 amps.
Just about every country has it own "special feature", so that people can point to it and say "Look, the wiring in other countries just isn't safe, 'cos they don't have this feature"
This sounds like it could be the Spanish one...
Just curious: Does the consumer unit house fuses or MCB's? Does it have an RCD?