Ah its good to see the eth (ð) and i (æ) outside of my Icelandic studies. French did a lot of "damage" to languages all over Europe during the late middle ages, one of the reasons I'm enjoying Icelandic with no real outside influence beyond the Danish trying a little bit.
English and Old Norse were spoken along side each other for ages in Britain, especially back when we had Norse kingdoms (like Jórvik) and Danelaw. All in all, its a shame we lost some of those extra characters which as I understand it, started to happen when the printing press came out. The Dutch machines didn't have ð or so instead they'd use th, and thus began the end.
An anecdote I've come across (which might not be true) is the fact the "ye olde sweet shop" should in fact be "e olde" but because the machines didn't have the thorn () char, they just started using y at first before using th.
Ah languages, gotta love them. Oh, if you like languages and use Linux, google for the compose key!