Hmm. All IMO...
Someone like Dave Wilson could do a pretty good fill and match, and you can probably pick up an original Antigua guard for £100-ish. That's a lot of money in total, though.
The alternative - like you say - would be to refin it. It's already been butchered so you don't have to worry about keeping it original. Plus, Antigua isn't really that popular in the second hand market anyway.
It's a toughie, but I'd maybe be tempted to go with the latter.