Here's the thing:
The OP hasn't answered the question with regards to when (or if) his former wife was asked either by the Judge at the hearing or by his Solicitor about being in another relationship. Neither has he noted if he was also asked that question.
I'm nigh on 100% certain that neither of them were asked to state this fact via affidavit or in response to questions at the hearing.
And why might that be?
Because it's not relevant.
OP may be feeling very aggrieved (understandably!) that his former wife was possibly unfaithful during their marriage. However, the conduct of either party during the marriage is not taken into account when reaching a settlement - unless (and this is a big unless) it would be a grave injustice not to do so. As an example (I stress the word example) of grave misconduct you could be looking at criminal activity, domestic violence, convictions for serious offences. Adultery doesn't make the list.
If the OP is paying spousal maintenance, then that will cease if his former wife remarries.
EDIT: to keep noproblem happy - IANAL