UK/Canada immigration questions: Who do I call?

I have a question about the immigration rules between Canada and the UK. I am trying to call a few places to ask this question but no one seems to be able to help me (UK border agency, British high commision, ect).

I have recently returned from the UK where I spent the past two years there on a working/holiday maker visa. I am wanting to return to the UK as soon as possible; however, I am wanting to travel to the USA before I do so. I am just wondering if visiting the USA during this time would affect my chances of getting into the UK. The reason why I am unsure is that I have been out of my home country (in the UK) for two years and I am not sure if I have to remain in CA for a certain period of time before I can travel again.

I have tried posting this question a few times here on the forum and I haven't gotten a response so I am hoping that at least someone can suggest a place that may answer this question or a phone number or something.

So, does anyone know who I can call about UK/CA immigration rules?

I appreciate any advice