Originally Posted by Globaliser

Welcome to (posting on) FT, belfastgt!18,000 Avios isn't going to get you very far. Perhaps the best use of them is for two short round-trip short-haul tickets, assuming that you have collected at least one Avios in the last year and therefore qualify for Reward Flight Saver pricing.

Off the top of my head, I think that you can't use Avios to upgrade a cash ticket on Aer Lingus.

I suspect that you're going to be pretty hard pushed to find any BA long-haul route on which 18,000 Avios would get you an upgrade to business class. On the short trans-Atlantics (eg London to New York), you'll get an upgrade from a paid-for business class ticket to First, but that does depend on you buying that business class ticket with cash first. See this chart, from this post:-