Liz,
Just got back from Lostock.
I am so jealous. Wish I could go with you! I have been to the places you've listed, except, Switzerland.
Whilst you're in the Czech Republic, make sure you get down to Cesky Krumlov, if you can. It is an absolute treasure.
And, here's the Colosseum picture:
http://users.tpg.com.au/octane2/ilcolosseo.html
If you'd like to attempt what I've done there, the only advice I can give you, is get to the location you want to image from, well before when you want to take the photographs. The place gets very busy at dusk.
I hope you have the best time, and, am looking forward to your images.
Regards,
Humayun