I've not renewed my fictionwise club membership this year as it's become increasingly difficult to get books due to geographical restrictions. Even though it's not directly their fault they're just applying the restrictions they've been told to they've lost my business due to this.
I wouldn't use any kind of proxy to work around this. Man in the middle attacks can be used even on an SSL connection. You're risking the theft of your C.C details and other personal information even though you may get the book you purchased. Whilst you should be able to detect when this is happening, it's not "obvious" unless you really know what to look for.
http://www.securityfocus.com/brief/910
Personally I wouldn't touch proxies with a barge poll. Let fictionwise lose money, don't put yourself at risk. Besides, if you buy books that have geographic restrictions, Authors/publishers will not see a drop in income and have no incentive to sign world wide deals.