Thank you all, you all have been a great help, making the whole process incredibly enjoyable.
I have taken it for a quick ride with the old exhaust and it is a monster! Quite heavy to manoeuvre not under power, but once it gets going incredibly quick. Particularly over 3000 rpm it takes off and the brakes are FAR better than my KZ1000P's which I imagine is what the original KZ1300's are like. But as the engine is essentially new, I need to be careful with the revs for a while, so haven't opened it up completely yet. I expect to be scared sh*tless and/or blown off!
I still have not heard from my insurance company so can't take it out for a ride yet - and we are in lock down now, so the coppers WILL pull me over if they see/hear me - but for certain a riding video will come.