Personally I would want the taxi fare back in full (minus perhaps whatever you may have paid from the airport to your Dublin venue), but I wouldn't be bothered about the Avios (I'm quite rich in Avios). As was pointed out by MickV, £200 is almost a bargain fare. I guess you could have shared it with AN Other passenger however. Anyway, added together I see it as fair and reasonable, particularly given the mega fast response - which is also worth something.