Hi Lou
The best way to manage chronic pain is to keep pain medication well topped up. It doesn't work as effectively if used "as and when required". So don't wait until you have the pain at it's worst! It really does need managing and what works for one doesn't work for another.
Diclofenac is a Non Steroidal Anti inflammatory Drug. This means its primary concern is reducing the level of inflammation which in turn should help a little with the pain. It should be taken on a regular basis following the prescribed guidelines specific to you. A stomach protector, such as Omeprazole or Lansoprazole, should also be taken alongside any anti-inflammatory drug.
To get the best benefit from Co-codamol you might find it helpful to develop a routine that suits you. For example two tablets after breakfast, two at lunch, two at teatime and the last two at bedtime. It really does need to be kept topped up for you to experience the full benefit. At the moment I take CoDydramol (paracetamol and dihydrocodeine) throughout the day and the stronger Cocodamol 30/500 at night. I now manage to 'save' my afternoon pain relief so that I can take a dose in the middle of the night, if needed.
Driving will certainly irritate the joints so this perhaps isn't helping. Certainly, as Sheila suggests, physio referral would maybe be a good way forward as there are exercises that will help with neck, shoulders etc. That said, a physio won't be able to help until you get the inflammation and pain under control.
Hope this helps in some small way

I know just how it feels as I have a lot of joint damage as well as ongoing active disease and pain can be very wearying. But you have the stuff to sort the job but you do need to take it rather than look at the box!!
Let us know how you go on. Good luck Lou,
Lyn x