Thought I would give an update to this.
6 weeks ago I had the operation to pin my collar bone back together. When I first went to the fracture clinic I was told that collar bones heal themselves and I should just leave it. From my research and asking people on here I think that advice is fine if your break is still in alignment. Mine was about an inch out! I would have been in a sling with little movement and no driving for at least 8 weeks. I explained to the doctor that I was very sporty and needed this fixed properly and after a bit of a conversation he went to speak to his consultant. On his return he said it was bad enough that they would be willing to operate and so far I am very glad they did.
Within 3 days of the operation I had a good range of movement and really reduced my use of the sling. Within 2 weeks I was back on the road bike being very careful not to crash! Bumpy terrain was too sore. The last 2 weeks I have been able to ride my gravel bike but sharp jolts are still quite sore. I will not be on the MTB until March at the earliest, I cannot risk crashing and jolts are a bit sore too.
The physio was delighted with my level of progress and puts it down to doing the exercises and generally using my arm gently. I need to remember that the bone is not fully healed until 12 weeks so need to be careful for a while yet.
Yesterday I went to the climbing wall and did some very gentle climbing which seems to make my shoulder feel a more relaxed. So all in all I am very gland I got it pinned and if you are unfortunate enough to break yours I would push for getting it pinned.