Hello Duncan
I would recommend PVC coated 4mm stainless wire for your guard rails. See,
http://www.tcschandlery.co.uk/9...-Covered-Guard-Wire.html Standing rigging, I would suggest you unstep your mast, take off your existing stainless shrouds and stays, leave the rigging screws & any toggles attached to their respective wire, incase they need to be replaced as well, label them clearly and take them to your local rigger and ask their advice, but as a guide I should think 5mm 1/19 stainless wire would be suitable.
I would not recommend making the new standing rigging yourself, this is a job for professional equipment.
Running rigging, traditionally a low stretch polyester rope was used for halyards, e.g. King Braid. For sheets a soft hairy rope was preferred to aid grip by hand, e.g. Kingfisher 16 Plait Matt Polyester. But nowadays a lot of people just use what is called Braid on Braid for all the running rigging. This is a polyester rope with low stretch and is normally soft to the touch and easy to coil.
for examples see,
http://www.tcschandlery.co.uk/c/237/Ropes.html Sorry about the plug for TCS but they are local to me and seem to stock most things, they also do mail order and have a rigging service.
Hope this helps.
Mike Edwards
Seal 28 "Aztec"
Mike Edwards
Seal 28 "Aztec"