Yep, it's poor product support. I just exchanged another set of emails with them. They suggested I go to Bunnings and look for something to use instead! There are 30 of these on the cover, 20 have to be replaced, I can live with the ones on the end of the strap that go on the hook rusting but the ones used as a buckle are damaging the straps due to the rough surface. To replace I have to cut them off and then pay someone to re-stitch the straps to put new ones on unless I can perhaps use a key ring style that I can 'turn on'. I found some s/s key ring style on Ebay in China but I don't think they are going to be big enough. Might have to just order them and try them.
I might hit them up with a Fair Trading case yet on the basis that they are not fit for purpose - after all they are on a weather cover for a tent, they should be able to resist weather! I don't expect them to be perfect but they are becoming unusable in 12 months, a piece of steel with 1 coat of paint would resist weather better than these