Oh, I loved the James Herriot books as a kid (had no idea there was a mini!); I'll download your story for my plane ride tomorrow.

Your fandom selection suggestions are wise indeed! With some overlap with you, I have learnt three main things from my three Yuletides:

(1) As much as you may be familiar with the canon, the fandoms you want to request are not necessarily those you could ever write yourself. I enjoy watching Bollywood. I have watched a fair amount of it. I have practically memorized certain films, despite them being in Hindi. What I cannot do is write Bollywood fic. OUCH.

(2) Do not offer a source you hate or have significant frustrations with. This may sound like a given! But I actually love writing fix-it fic, and feel most inspired by sources I have big issues with. Yuletide is neither the time nor place for offers made from frustration, since the recipient probably loves the very elements you hate most. (I'm sorry, recipient-from-years-ago! I'm ashamed.)

(3) If you feel you need absolute control over a story in a particular fandom, avoid that fandom without regret. One year I offered Hotel Rwanda and Last King of Scotland without really looking at what characters had been nominated-- I guess I just assumed the nominators had grim political gen in mind like I did. NOT SO, MY FRIEND. Fortunately I had time to backpedal, but whew: I think I was pretty close to being mandated to write romantic white-person porn against a background of mass murder, yo.