Flashed the UK version with Odin, went perfectly.
Flashed back to HC, went ok but hung up on glowing Samsung logo.
Booted into recovery, did the wipe thing, and all was well.
Monday am, checked for OTA update, got the message available.
Did a reset, figuring it would give me a nice, clean install of ICS.
Checked for update again, got not available. Weird.
So, I did it using Kies.
ICS is running great. Very nice update.