//the new law which will provide for religious organisations to opt out of performing same sex marriages is very likely to be challenged (especially if the organisation concerned is the established Church of England) and a challenge, in my view, is very likely to succeed. //
as I read the BBC's interpretation of the bill, the CofE, as established church, currently has to conduct marriage for whosoever requests it. Thus the bill will expicitly ban the CofE (and the Church of Wales, unless the Lord Chancellor decrees otherwise) from conducting same-sex marriages, since doing so would contravene canon law (which itself has legal status). Thus legally the CofE does not have the opt out option available to it.
If that's the case, would such an arrangement be as susceptible to ECHR challenge as a religious order who chooses to opt out?