You wanna try the Sky Garden in 20 Fenchurch (the new walkie talkie)
2 restaurants and a bar up there, and an experience to behold! be pretty cool anniversary surprise that would be if you can get in!
failing that, you can get similar vista’s at the Duck & Waffle on the top of the Heron Tower which has Sushi Samba next door. always a good night.
another option is Madison on top of that shopping centre opposite St Pauls. has a nice roof terrace with stunning views. bit wankerish tho. more of a bar really.