Update
Went yesterday to INSS Torrevieja, handed in the S1 forms and received our document to take to the Medical Centre. Painless experience and very nice Lady dealt with us. Very busy there - we were no 78 in queue and it took 1hr 50mins to be seen.
So now need a few more copies of docs to give to Medical Centre for SIP cards.
All in all a very pleasant experience and summing it all up have come to conclusion that if your paperwork is in order then the process goes smoothly (in TORREVIEJA). Nice to have the expertise of this forum to turn to for help. 😊