One word: Patience
Hi guys thanks for the responses, since making my post the guy and I have decided to make our friendship open, i.e that instead of pretending I am an acquintance she will know if we go out and do things.... however just as friends, we are hopeing that in light of this A she will begin to realise that I am someone important to him and that B hopefully she will begin to trust me and continue our friendship and then at a later stage when we are all very comftable we will bring up the poly idea and talk it over, but in the meantime this new honesty has meant my time with the guy and our romantic contact via phone/ text has dramatically dropped, down to once a week seeing each other, I appriciate why (as if he was all of a sudden telling her we are seeing each other every second day she would get jelous straight away) but its so hard and to me it feels like a step backwards and that I've lost my lover.... I know that we have to do this in order to move forward, but any suggestions how for me to handle this change?
It seems that you have a possible configuration for polyamory, but you must build it from scratch. And you have already nearly blown it by starting off something definitely romantic without telling her. Would YOU like to learn that your partner has started a new and deep romantic relationship, weeks or months after the fact? If that would be quite OK to you, you are surely among the exceptions to the rule.
You have probably had huge amounts of NRE (New Relationship Energy) flowing. That's natural and a good thing (mostly), but one thing is for sure: It won't last. And you should start making up your mind about how much contact you want, and how much you need, as a minimum. Then you multiply by three, and see where you end up. Reason for the factor: She probably needs to see him somewhat more than you do, because of all they have together, and in a poly-setting, he must have a generous portion of time for himself too. And pressing the schedules too much is only likely to make everything wear out faster.
If you can't imagine a scheme that is probably satisfactory for her and still enough for you to thrive and develop the relationship, you should probably seek polyamory somewhere else. While love is unlimited, time and attention is not.
If you think there are some good or at least acceptable solutions, my opinion is that you should, in a modest and careful way, try to bring up the polyamory theme as soon as possible. But she must have the final decision about the steps forward. I think it is impoortant to realize that as soon as she gives her informed consent, you are de facto in a polyamorous relationship, even if you haven't entered the sexual domain fully yet. IMHO, what you and he have developed qualifies as that, only the openness and consent is missing.
Patience is what you need most of now.