When I went down to London with East Coast in October, I had a Class 43 HST on the 08:38 from Durham, so that would be the 08:20ish from Newcastle. From what I've seen, it's always a HST.
One thing I would definitely look into, Adam, is using the Flying Scotsman service. You know the one that starts at Edinburgh at like 05:40, gets to Newcastle for bang on 07:00 and arrives into King's Cross for about 10:00? Get on that.
I imagine it'll be a worthwhile experience. I'd absolutely love to do that! (Hintedy hint hint!)
Whats made you happy today?