I can't decide what I'm enjoying more, the series (if you think of it as a glorified soap, you can largely ignore the flaws) or this thread.
The Edith & Drake thing bugs me a bit. I don't remember much about him being ill in the first series so I can't be sure that Mrs Drake is his wife but as she's not Miss Drake, she must be his Missus I suppose.
But her behaviour doesn't suggest heartbreak or bitterness. When she's seen them having a laugh and then snogging she's merely looked disapproving and the letter to say Edith's services are no longer required seemed quite sensible, as it's quite likely they are tenants on Grantham land and may be at risk of eviction if the Earl were to find out about the shenanigans.
I found it weirdly disturbing that the married, older tenant farmer (who paid for the tractor? - looks like an expensive bit of kit) could be engaging in what appears like a quite innocent romantic encounter with the posh girl (surely it should be a bit more lewd?). It would all fit ok if Mrs Drake was his mum (or widowed sister in law) but as his wife, it boils down to Edith being a bit on the side.
I also think that O'Brien may turn out to be Joseph's mum - which of course begs the question, who is/was his dad? If she was in service at the time, it's likely to be someone quite posh?
If anyone can be bothered to read all this, I'd be interested to hear what you think!