I am just finishing 6 months in Europe doing some photo stuff among other things. Let me say first off that the first and most important consideration is your personal shooting style and aesthetic. Your lens choices will be dictated by that fact, so YMMV.
That being said, I faced the same question you do before I left the US and chose the 50 1.4. I thought I might need the extra range for some work I thought I might be doing. Long story short, that specific application never materialized (though the lense has been a wonderful portrait machine), and I really wished for a wider lense! This is mainly because some of the shooting situations call for extreme handholding in available light, so as short a focal length as possible is great. Also, shooting space is often very restricted, stuff here is much closer together and your back is to a wall pretty quickly, so wide is helpful to getting the shots you want.
Ideal (for me), in the digital crop world, would be a prime somewhere between 20-25mm, designed to be sharp wide open at 1.4. That would give a useful field of view (stuff is really tight over here compared to the US, wide is good), and could be hand held in available light at significantly lower shutter speeds than my 50 can be. I would like to get the Nikon 28 1.4 that apparently has just been discontinued, but I am now hopelessly poor
The 35 f2 would be next choice for me.
Lots of places (usually the best ones) here allow, no flash, no tripod and even sometimes no monopod (which is my next recommendation for you, GET ONE!). So you are reduced to shooting the interior of the most beautiful cathedral you have ever seen, or exhibits in a museum, at very slow shutter speeds.
When you can use it, a monopod rocks, especially if you get one with the feet that can be deployed. Folks don't notice the feet and if you are subtle and don't make a nuisance of yourself, you can deploy them and get some long exposures. This works best inside, as it is not steady at all in any wind, but it's a great thing inside or when it is still.
In one case, I was in a castle and they would not let me use the monopod on the ground...no problem...I shortened it and stuck the bottom in my jacket pocket. Because I had the ballhead on it, I could adjust the camera just how I wanted it. This made me extremely steady, perhaps even more steady than just putting the pod on the ground without the feet, especially when I would kneel and press the foot into my leg. So I highly recommend one...I bought mine here after finding my 50 1.4 not getting the pix I wanted and needing some way to get more steady.
So the short is, in my opinion, go fast and wide, and get a good monopod. Good luck!
