I think talk about 'two gospels' in the Communion is something which bears some careful scrutiny.
First, we need to take into account that 'the gospel' (as told and taught in the New Testament) is a gospel told in different versions (Matthew, Mark, Luke, John, and Paul ... the writer to the Hebrews, James, John the seer as well?). These variations are not insignificant. It has been observed (though I cannot recall by whom) that the Roman Catholic understanding of the gospel rests more on Matthew than on Paul with much argument and conflict ensuing through the centuries. With respect to the Communion, a claim that there are 'two gospels' needs to check carefully that we are not talking about two versions of the one gospel rather than two gospels.
Secondly, we need to ask when differences in the understanding of the gospel affect fellowship and when they do not. Over the years I have had concerns about what fellow Christians believe to be the content of the gospel - sometimes in Anglican contexts, sometimes in ecumenical evangelical contexts (we use to have lots of vigorous discussion in the Christian Unions when I was a student at uni), sometimes in ministers' fellowships - but I haven't broken fellowship. In hindsight I think this was a very good thing not to do because with patience and listening I have come to new realisations about what the gospel is, including the realisation that my understanding can be improved and that others' understanding can be interpreted differently from my first reactive response. In other words, some differences which at first sight might look like "fellowship breakers" may at second sight not be so, so much care is needed.
Thirdly, we need to keep a sense of proportion. Over in England at the moment the Church of England via its flagship St Paul's Cathedral is taking a huge hit because the authorities in the cathedral (as best I can make out) lost a sense of proportion. In upholding the rules of health and safety they have allowed themselves to look to all the world like the moneychangers in the Temple rather than like Jesus. If our greatest concern about 'two gospels' is (i.e. boils down to) a concern about homosexuals, and if that concern is going to divide a church or the Communion, have we lost our sense of proportion? I think I share most concerns conservatives have about +Gene Robinson's consecration, the blessing of same sex partnerships, and the ordination of people in those relationships, but I (seem to) differ from some (many?) conservative Anglicans in my unwillingness to leave the Anglican church over these matters. For the life of me, I cannot see a good sense of proportion being worked out if I find myself in a new church which is largely defined in its distinctiveness because of what it does not approve about homosexuals.
Now I am pretty sure that some readers here will read all the above and say, Nevertheless, there are two gospels in the Communion today and unless something is done about this, the Communion will divide formally and (eventually) completely.
Yet there is still something to think about in respect of claims about two gospels ... to be continued.