Welcome to the Org, Rhubarbmisterwellington . I hope you will enjoy your stay here.

Quote Originally Posted by Rhubarbmisterwellington
Now - finally (!) some questions:
When I watch the taking turns screen, I often see a progression of enemy agents appear from nowhere, enter a city and stir up civil unrest. Some cities are maxxed out on happiness/law bonux buildings, have a govenor that isn't too venal, a garrison (not too big of course) and a coterie of all three types of agents, yet are constantly suceptible to enemy agent attack. How do I stop this, and for that matter, how do I do it back?
Placing one ore more spies (preferably with high subterfuge values) is the best way, as Dutch_guy pointed out, but what I think you see is one or more enemy spies being expelled by your spy and then trying to reenter. Your spy is apparently not good enough to catch them, but his presence forces them out each turn. If this is correct, you should get a message each turn that a spy was found, but escaped.

Why when I take a city and put the population to the sword/ship them off as slaves, do I face unrest and culture penalties? Surely the incoming population is from my own lands and consequently loyal - and of my own culture? Any ideas?
Culture penalty is determined by the number of "foreign" and own buildings in a city. IIRC it maxes out at 80%. The most important building is the governor's building. So yes, you do face them, but because the population is small a garrison should be able to supress it easily.