Having visited London lots and Paris recently, I didn't want for tele ranges... Most of my pictures are with the 16-35 & 24-70 ranges, both f2.8 - I didn't really feel a desperate need to go wider and I do like to shot at 16mm. I've recently packed my lensbaby fisheye, which gives me a circular image on full frame, it's not expensive, quality isn't great compared to my 24-70 but it's fun - you could look at a cheapo fisheye from ebay as an alternative.

Re tripods, just don't, it's too busy, take a mini desktop or a beanbag instead - I'd always pack some ND's for the river shots, spokeless London eyes and traffic free streets. I'd also take your EOS-M as Paris in particular is really dodgy at night and at all times there's pick-pockets and Eastern European females trying to scam you asking if you speak English as a distraction whilst another rummages through your backpack.

Best photo sights ? Science & Natural History Museums, Louvre, Greenwich, Sacre Cur, Notre Dame, Canary Wharf, plus do the river tours, avoid the bus tours, you can't get a good photo on a bus.