hi alan,
that doesn't sound like much fun!
there sounds like rather a lot going on, but you are quite correct in wondering if the problems can all be inter-linked - the human body is a finely tuned machine! i suspect if you had the neck symptoms first, however, that the lower back may be secondary.
a few ideas for you:

- many of the symptoms you are describing fit within a condition called cervicogenic dizziness - the muscles in your neck contain the highest density of muscle spindles of any muscle in the body. they also provide a lot of information to the brain to assist with maintaining your balance and clear vision. i find patients with CD describe a constant lightheaded/muzzy/floaty/nauseous feeling and often have issues with motion sickness.
- a quick test (you are going to think i'm a bit mad - but oh well) to have a look at how well your neck detects joint position sense...tape a laser pointer onto a bike helmet and put it on. sit facing a wall about 90cm away. stick two pieces of masking tape on the wall 80cm apart with X's drawn on them. point the laser pointer at one of the X's, and in one smooth movement move it to the other X. return to the first X. close your eyes and then try and point the laser at the second X. open your eyes and see how close you got - a difference of greater than 4-5cm is considered 'abnormal'
- abnormal cervical spine JPS can lead to an increase in muscle tension as the neck muscles are constantly trying to correct your posture and react to movement.
- if yes, it could be worth mentioning to your physio. you can rehab it.

it sounds to me like you may need an assessment by a vestibular PT - it's difficult for me to diagnose you over the internet, and often people can have a combination of issues. they can at least give you a bit more direction and prescribe you a self management plan etc etc.

hope that helps!
cady