I think I read that the vicar was doing 4% marriages over the year, then this shot up to 300%, so legal marriages were not the priority.
But the wedding needs witnesses, so who were the 2 standing up for this? When I was a witness at a wedding, I wasn't asked for any ID, and could sign anything I wanted to.
I think most people could be 'bought', at a price, if their logic deems that they would get away with it, but the bigger the fraud, the bigger the lie, so eventually, if sucessfull, the scam fails.
There is probably some legal loophole to say these people were married, and it is legal, and entitled to remain in the UK, due to an appeal process, then time running out for a certain law to apply.