I'm afraid I have some bad news...
Unlike the Mac, where this 'recently used address' list can be editted, on the iPad it can't. It annoy almost everyone but there's no way of deleting entries from that list. The only - partial - good news is that this list is of limited length and entries eventually 'drop off' the end.
Tim
Thanks.... it is very annoying especially when I have mistyped in the address the first time and the system keeps suggesting it... over and over...