Fixed mine today, that's another niggle off the list

Lock not fully opening was just a case of needing lubricated, quick squirt with WD40 and it worked properly first time. Used it a few more times, allowed some time for the WD40 to soak in and gave it another good spray just to be sure.
Outside handle not opening was a little more involved. First tried sussing out the mechanism with the little "gear" which the handle uses to rotate a rod across the top of the handle inside the door panel. I initially thought rotating this a tooth would cure it, as the handle was at the top of its travel and still not moving the release mechanism far enough (easily evidenced by pulling the inside handle which works perfectly). A little more investigation discovered the rod near the back of the door, which connects the handle mechanism to the release mechanism, appeared to be out of shape. Access here is quite limited as is vision, but I managed to release a little plastic clip on the handle mechanism which allows the top of the rod to slide out sideways. The bottom part then just lifts out.
I'm surprised this has gotten out of shape, as it's very sturdy. I guess though that 8 years of use and abuse had taken its toll. Into the vice it goes and a few taps with a mallet straighten it out so that it will have more reach when operated. Refitting is the reverse of removal, just pop in the bottom part, slide in the top part, and importantly make sure the plastic clip at the top is secured otherwise the rod will probably fall out after the first pothole!
The door handle now works a treat, opening the door around half way through its travel angle similarly to the other doors, unlike previously where it would be almost at the limit of how far it could be lifted before the door would open (until it finally gave up and wouldn't open at all).
Unfortunately my check strap mount is still broken, but that's way beyond my level of ability!