Hiya, used to fly from Barton too and am resuming in the new year to fly from there. With regards to this piece of airspace I must admit it is not great but it is not difficult to navigate using good old DR and keeping VERY watchful of heading/drift/altitude. There are sadly IIRC no handy line features to follow but quite a few landmarks. The danger of collision is undoubtedly higher here than in more open spaces but again just keep as good a lookout as you can (and hope the guy coming the other way is doing the same!). Have you flown the corridor with an instructor?
With regards to your trip to caernarfon, why not try Liverpool for a zone transit and have the low-level corridor planned out if refused, or as you say, a route round the north and back down if you prefer. Have done this trip quite a few times and always been allowed through the Liverpool zone.
Beet.