The RareTV copies were missing at least a couple of episodes and the company was awful to deal with, selling very poor quality material for inflated prices. The series was also available from an obscure auction site as a complete set which was better quality than the RareTV set and was 1/3 of the price (Matt, did Ben let you have a copy of this set?).
I've managed to find this site again:
Wings ,Complete BBC TV series 1977-1978, WW1 For Sale