I watched the first episode of Partners in Crime and I stopped after that;

Wise woman! I didn't think it very good, but it was entertaining enough for me to keep watching.

And Then There Were None was a much better adaptation.

Yes, less messing about and better casting.

Towards the end, I was thinking that if Vera and Lombard had teamed up, perhaps they might have been able to catch the real killer had she not panicked and thought that Lombard was the killer.

Yes, they were definitely dangling that before us, I was thinking the same between having the first two parts and watching the third, but, Vera was clearly unravelling from the pressure.

I've found a copy of the book and will probably read it to see how much was changed.

You say you love mysteries, and I know you like period drama. Did you see The Bletchley Circle at all?