In reply to Šljiva:
The one in Nant Peris is very basic. Showers a bit depressing. No loo roll supplied. On a positive, £5 a night and opposite a good pub. Good for a night or two.
You can camp up near south stack somewhere, again basic but handy for the obligatory late finishes at gogarth.
The best I've stayed at is about a mile from bethgellet. v beautiful site with great facilities but probably busy with families this time of year and pricey. Kinda half way between pen y pass and erics. If lucky you could pitch near the stream at far end of site.