Detectorists is amazing.
The recent Thatcher series is brilliant as well.
Blackadder & Royle Family - all of them are available.
I have a soft spot for Miranda but know that everyone else on here hates it.
For anyone with preschool kids:
All 3,485 episodes of Bob the Builder plus Twirlywoos and Hey Dougie are examples of how utterly without peer CBeebies is.
I watched the bloody Godfather on iPlayer last week. Casablanca as well. Ridiculous.