Anyone fancy lending me a hand here;
I'm looking for something, anything to disenchant to get the Fortify Heavy Armor enchantment - I did have a few '____ of ____ Knight' items but I stupidly sold them off...
Does anybody know a definite place to find something with that enchantment?

If you got the gold, just shop around and buy a cheap item with the enchantment. They aren't terribly expensive if you have a means of making the gold back.