>I'm also able to make the£ with ALT-0163.

this probably doesn't warrant much space, so I'll try and keep it brief: the original 7-bit US ASCII code didn't allow much room for expansion so there soon developed several national versions (all these were controlled by the ISO 646 standard); this was very messy and was superceded by the ISO 8859 alphabet soup which is an 8-bit standard in which the original 7-bit ASCII truly was standardized and the various national versions were incorporated in the expanded set; this is now being replaced by so-called Unicode (ISO 10646), which is the de facto HTML standard -- our confusion is that there are many undefined codes, in this case (decimal) 0163 is the official code for the £ while anything else you may discover is highly untransportable and could change momentarily.