Does anyone why (or so it looks to me) none of the promos between programmes are in HD?
For that matter, none of the circles idents look particular sharp, apart from the animated logo - even "Channel of the Year" looks decidedly SD. They date to around the same time as BBC HD, so I'd always assumed they'd been shot in HD.
So - as far as the promos go - is there still some small part of the Beeb that's refusing to go HD?

Or is it something to do with playout?
Not a small part of the BBC, a part of a separate company. The promos aren't made by the BBC, they are made by Ericsson (formerly Red Bee) who are contracted to provide creative services to the BBC (a legacy of when BBC Broadcast was in-house before being sold off to become Red bee). The current contract is for SD promos. So the promos are in SD. It's a simple contract issue.
However the BBC are, I believe, bringing creative services back in house at some point soon (they have already advertised for the post production tender for it I believe) so I'd expect promos to go HD when this happens.
You will see occasional HD promos. These are usually short bumper type promos made by the programme themselvess on-the-day for live and close-to-live shows like Watchdog, The One Show, Question Time, Springwatch etc. These are made in HD and fed directly to playout without going via Creative Services.