Raleigh may have a proud British heritage, despite being sold to the Dutch, but the Sojourn has American ancestry. It's been available across the pond for some years now but it's taken a while to find its way here. Style-wise it takes a few cues from recent North American disc based touring machines with a touch of MTB in their DNA. Think Kona Sutra or Salsa Vaya but with a slightly less compact frame.
Using a drybag as a lightweight saddlebag is the topic of the latest post on the audaxing blog
In a sense there is no point in doing this for weight saving (even though it saves a whole kilo) as the bag will contain lots of heavy stuff. Also it's nothing compared to the vast bulk of the person on the bike
Anyway, drybags are great and worth considering for bike luggage