"That's the thing, I can connect fine to my folks wireless, and to my mates Orange one, and he has the same router and provider as me (Though mine is older as it has the old name on it), and to most other ones I've tried.
I've mentioned this before in other forums, but it's nothing to do with my DS being from America is it (I live in the UK)?"
As far as I'm aware the DS is region free, though I'm not 100%.
You may have the same router/provider but your security can be different. For example my BT was initially WPA security (more secure than WEP) however I couldn't connect my DS/Wii to it, so I change it from WPA to WEP and it was all fine. Though when changing your WEP key, you'll have to reconnect anything that connects to the internet.
If you have a PS3 and go to connect to your internet it'll say what security it is. I don't know if the Xbox 360 is the same.
If you're still unsure, you can always ring up your provider for further information/help.