I held off when it was £7.99 in the other deal so picked this up. £5.99 for prime members not sure how much postage is for non-prime. Says in stock on the 25th Jan so obviously not ideal if you want it right away. Amazon often gets stock in before the date advertised though.
Firefly Complete Season blu-ray US Import £5.99 for prime / £7.98 non prime @ Amazon