Following advice on various forums I'm hoping to redeem some BA Avios on trip to New York, flying economy with Aer Lingus. Problem is I'm not sure what the taxes are to compare my options. Looking on the Aer Lingus site the taxes are €96 (fare is €528) but on Avios web-site they are £183 (+40000 miles). Why the discrepancy on same flights and class? Which would I be charged if I rang BA to book?