Multiligual Website Culture Settings?

In asp.net multilingual website in english Uk and swedish, i have three rsources file

1. en-GB.resx
2. sv-SE.resx
3. Culture neutral file.

I have create one base class and all pages is inherited from that class. There i write following lines to set UICULTURE and culture

1. Thread.CurrentThread.CurrentUICulture = CultureInfo.CurrentUICulture.Name;
2. Thread.CurrentThread.CurrentCulture = CultureInfo.CurrentCulture.Name;

Question: Suppose my browser language is Swedish(sv-SE) then this code will run because it find CurrentUICulture and CurrentCulture values as sv-SE.

Now if suppose browser language is Swedish(sv) only, in that case values will be set as

CurrentUICulture = sv; and CurrentCulture = sv-SE

Now the problem is that user can able to view all text in Culture neutral resource file that i kept as english while all decimal saperators, currency and other will be appear in swedish.
It looks confusing to usr.

What would be right approach. I am thinking following solution.

1. i can create extra resource file for sv also.
2. I check value of CurrentUICulture in base class and if it is sv then replace it with sv-SE

Please correct me which one is right approach or Is there any other good way of doing?