So overnight I had a chat with a guy thats not only restored one but who is pretty much the first guide who comes up on google, the bolts failure was likely an attempt to remove it without a Sash clamp in place to take the tension off as yes that whole plate at the breech is under tension, theory on cocking could be simply the seer has become fouled.
Parts with its washers/seals and that's your lot mate so Old Man or a turner will be required to make a new bolt (I'll show why off the shelf wont work), hopefully seer is indeed fould otherwise thats a patch up, measure and have made which won't be a cheap job if Old Man cant do it, I think springs are alright as it bit me a few times trying to get it to recock.

As I've been stuck awake I did also take the time to file a slot into the damaged bolts exposed side and hopefully later on I can get the sash clamp on and get things progressed, wish me luck lads.

PS, Paperworks got me pondering, I'll show you later why.