Well I have almost the same problem and I live in Denmark. Sometimes when I play on the public server I have a ping around 100 on a good day. The other day it was about 170 on the public, so I find it kind of weird that from one day to another my ping went from 100 to 170. Also on the private server I have issues, the other day it was way over 200 and the other day it was lover than 200. So it seems like I have some of the same problems like Branem. I really hope to find a solution to this issue.