Soldato
I gotta tell you I wouldn't have left a main road into a fully separated layby either. That's ditching all momentum and coming to a full stop to reassess the road before rejoining it.
They wouldn't need to stop, merely pull to the left for a few seconds and let the other road users pass, no loss of momentum or inconvenience to anyone but a cyclist doesn't see things that way clearly, they want it all their way with vehicles giving safe space when passing but won't work with other road users.
Depending what the road is, I would be more worried about the rejoining bit. It's quite hard to get a good, proper look at what is actually going on behind. Sure, pull aside, slow down and into the layby... then get hit be the second person coming through as you rejoin the road...
On a country lane where I can get a good look behind, its only a car and I can see nothing else behind is a little different.
Often I prefer to keep as left as I can and just be as steady as I can. As long as I'm not acting unpredictably, not being funny, it is the car behinds problem to deal with. If me trying to deal with it endangers my life, the person behind is in a better position to act.