I have a Cotic Solaris (Mk1) that I use for bikepacking and long distance stuff. Cotic have just announced the Mk2 Solaris and they are selling off the remainder of the Mk1 frames though they don’t have all the size range. Both versions can take 650b+ wheel/tyre combos as well as normal 29″ ones though the Mk2 is designed with that in mind.
There’s no one typical “bikepacking bike” though many go for the simplicity of a rigid 29er but equally some have full-sussers. At the Yorkshire Dales 300 there were no full-sussers, nearly everyone was on a hardtail or rigid bike. There was one fat bike and one crosser. Two were on singlespeeds.
The On-one Inbred 29er frame is just £150, you could build a nice bike up on that. The first guy home in the YD300 was on a rigid On-One Lurcher. There are one or two complete bikes about (Genisis Longitude for example) that are aimed at bikepacking.
Worth asking over on http://bearbonesbikepacking.co.uk/phpBB3/index.php as well. I’m on there with the same username, Stuart the guy behind it also posts on here. There’s a lad on there, Ootini, who has a blog where he’s doing bikepacking on the cheap.