Hi Ewan,
You are correct in your findings! The original parish church and burial ground (kirkyard/churchyard) was where you say it was, just opposite the castle.
The publication "Avondale Death Records" was transcribed from the micro-film record purchased from the Registrar-General of Scotland by Lanarkshire FHS in 2005.
I have driven past Kirk Hill in Strathaven (where the burial ground is) countless times but yesterday I made the trip over there especially to have a look at the stones, in the hope that I could reconcile at least one of them to one of the entries in the Avondale book.
It was a scorching-hot day yesterday and much too hot to be walking around outside, so I spent an hour taking photographs and then I was forced to take refuge in a conveniently close hostelry. (Tough work but someone has to do it).
I was involved in the production of the Avondale book and the unique style of recording the positioning of the deceased within the plots has always intrigued me. I have never seen "breadths" any place else. Why not "lengths"? It would make more sense but, after viewing the layout of the old burial ground and seeing just how steep it is, I have a theory.
Gravestones in country churchyards were very uncommon before the second half of the 17th century, they were for rich folk and Avondale parish was full of tenant farmers and weavers, the Duke of Hamilton was quite possibly the only landowner in the parish and he and his family were all tucked-up in their own private burial aisle in the old Collegiate church down in Hamilton.
So, perhaps the good folk of the parish were always positioned in the direction of the hill, head towards the top, feet down, if you know what I mean? Rather than laid across the land.
Then, when headstones (and table/flat stones) began to appear around the end of the 17th century, they were placed, not at the head of the plot, which would make them easier to give in to gravity as the ground settled after each opening but, were placed at the side of the plot, making them less susceptible to falling over on steep, uneven ground.
The earliest stone I could find was dated 1717 but I didn't look at every stone. The higher you climb, the newer the stones are and, once at the top it's a few steps over to the new cemetery on the other side of the hill.
I'll post some pictures and, once I get the time to edit them, I'll post a list of the stones I have photographed. What I did find on quite a few of the older, marker stones was the number of breadths the owner had in the plot. Just to confuse me (yes you guys, I know it isn't too difficult to do) one stone had "Three lengths and two breadths".
Picture of the castle, then the entrance, complete with the obligatory Rowan trees, always planted at an entrance to anywhere, home or burial ground, to ward off evil spirits.