Love Detectorists and have the first three series (seasons) on DVD, but I have to rain on your parade and say I found both Christmas specials dreary. Problem is, they keep covering the same old ground each time (if you'll forgive the apt metaphor), only this time they slashed and burnt everything first.

Morse is one of those things where there are some stand-out episodes and some boring ones. I loved its spin-off Lewis for a long time then eventually tired of it. (I tend to overwatch things until I can't stand them any longer). If you like Rachael Stirling, catch the Lewis episode with her in. It's possibly the best one they ever did. It's called Life Born of Fire.