Problem with UTF-8 encoding in requests

This is the problem our team is having.

"I have a request that is supposed to be UTF-8 encoded when it is sent. We are testing with the following ‘¥£€¢₡‘ it is expected that this would be ‘\uC2A5\uC2A3\uE282\uACC2\uA2E2\u82A1’ but we get ‘[0xa5][0xa3][0x80][0xa2]?[0xa0]’ after some investigation this looks like either Window ANSI 1252 or ISO Latin-1 (iso-8859-1) but not utf-8. I’m not sure how to fix this as there does not appear to be any way to change the encoding that is being used. In the NVP instance i’m pre-encoding the string to be application/x-www-form-urlencoded; charset=UTF-8 using groovy but i’m not able to do this for the application/json; charset=UTF-8 at the moment."

The log of the issue is the following:
<log was removed>

We are seeing this behaviour when the tests ate running from a Windows XP machine.

Can you please advise if there is a solution or if this is a bug.

Thanks,
Gordon.