I think I remember seeing those two along with several other Season 5 episodes listed under May 2007 for BBC Two on the Genome website. We still need to find the correct airdates for those last three Season 1 episodes though.
I think I also remember that Postman Pat and the Greendale Rocket did air on BBC Two in late 2003. It was headed as the "Critics Choice" in the Sunday Times. As for those two episodes I saw in May 2007, it was on the 7th and 14th that I saw them (I had a off school on those days). If the Genome website says the same, it may be best that you stick with it for now.