The previous episode (Get Out of That, Then) was originally aired 31 August 2008, and "Some Adventures of the Inventor of the Mother Stitch" was originally broadcast 19 April 2009, so "I Was a Hitman for Primrose Dairies" was the "New Year" Special on 31 Dec 2008, and as all specials, gets ignored in the sequential run... you'll have to wait for a bank holiday!
I contacted UK Gold by mail when this first happened stating there was no background on Hobbo which we learn in episode 1 of series 30 it appears to the uninitiated that he dropped out of the sky and without the use of Alvin's hang glider . When I first contacted them they sent this twaddle
I'm afraid there is no oversight this time around, this episode was
originally broadcast 31/12/2008,(Episode 2 which is actually the start
of series 30 didn't broadcast till April 19th 2009) it's a Christmas
Special, as such we won't be broadcasting it this time around, when we
broadcast Christmas Specials outside the festive period we generate a
lot of complaints.
So I wrote back and told them that although shown at Christmas time it was not a Christmas episode per say and received this
We have looked into this and found there was a historic discrepancy
in the way the distributor had labelled the series, which meant we
didn't have this episode available to us. We have rectified this now.
For future airings of Last of the Summer Wine, we will be including
this episode in the run but weren't able to include it this time
around unfortunately.
Clearly this time around and maybe other of the series replays they clearly forgot they had acquired episode 1 and did not keep their promise in the mail.