Thanks for all the replies.
Time permitting, I'll have a go at taking it all apart this weekend (putting stuff back together will be a whole different ballgame 😬)
Some further questions then -
1. If I've understood correctly, with the two bolts / bobbins holding the exhaust to the car out of the way, the connection between the primaries and collector is just an interference fit and gentle use of a persuasion stick will separate the two
2. I've read elsewhere about slight exhaust leaks after taking an exhaust apart. I'm sure I've read that silicone sealant should not be used - what is the correct kit, and can it be used between the primaries and collector, or just on the can end cap?
3. As per the question from Grim, is the 2nd photo from mechanicalmoz what I should be looking to achieve, or is that a bit overpacked?