'warranty' vs 'guarantee'

I’m writing an ad, and I’m trying to be culturally sensitive. Do the brits always use ‘guarantee’ when they mean ‘warranty’? Are they upset when they see it the superior American way? And what do the Australians say on the matter?

Bonus question: is ‘warrantied’ a word?

In the UK “guarantee” is usually used when referring to the standard 12 month cover offered by the manufacturer or retailer. If you want to take out extended cover then, for some strange reason, the term “warranty” is used. I have a feeling that this is yet another case of an an Americanism creeping into our language as guarantee has a slightly old-fashioned feel about it.