The cheapest way is likely to be for the new owner to fly over and take the dog back as Excess baggage, Cargo charges are likely to be higher than a cheap flight KLM/Air France do a set price for this method I think it's about E250 for the dog.
thanks brainless. Think i'm going to have to drive over with her. I wasn't keen on sending her over on the plane anyway. She's going to family so i'll just use it as an excuse for an extra holiday :)