To report back, I did do the FNC-Santa Cruz walk out and back. It's not an overly pleasant walk but it's very short, taking me less than 20 mins from Santa Cruz village centre to the terminal. There is a solid pavement all he way (I used the northern side but it looks like the southern side would also be possible), separated from the dual carriageway by crash barriers, and the actual bit on the dual carriageway is very short (c 5 min), the rest being on quiet minor roads. I'd do it again, no doubt.