Consent Order Lies

My ex stated that he did not intend to live with his partner in the next 6 months on the order

I knew he was already doing this and his solictor advised he was not in writing

I reported them for benefit fraud and this was investigated

His partner was investigated and it was found he was living there (no surprise!)

He has now admitted to living there officially (exactly 6 months after)

My whole Consent Order was based on the fact that he needed the funds from the sale of the house to house him and the kids which clearly he didn't

How can I approach this to remedy the crappy deal I was given?

It's unlikely to make any difference.

Courts bear in mind that new relationships are likely to fail plus he will just say that at the time he didn't have any intention of cohabiting, it was a later decision.

Hope its OK to reopen an old thread, but does it make a difference if someone is planning to marry and has declared that intention and/or started make arrangements?

It would depend on the whole circumstances.