I must add my tuppence here as well.
I had a set of vipers on my 6 when they first came out, rode upto skeggy and ended up getting a flat en route. The next day (Sat) I rang around for a new one and noone around those parts had even heard of vipers! Spoke to the nearest Avon dealer and they were miffed that they hadnt been told about them either. Ended up calling my dealer down south that fitted them, they got onto avon for me and within the hour I had the Northern England rep calling me. He couriered a new tyre up to a local fitter and had it fitted free! They then asked for the knackered tyre and sent me another new one as an apology.
Two months later I managed another flat, the tyre tread was very close to the limit, local dealer said about 300 miles left on it. Avon only went and replaced that one free as well!
IMO they have an amazing customer service, well done Avon