When you say the sale date, do you mean the date that the property must be put on the market? As that date hasn't yet passed, there is no breach - and while you think the ex may be obstructive regarding the sale, again that hasn't yet happened (in the context of the house being on the market) - so I can't see what there is to enforce at this stage. You would need to wait until the house is up for sale and the ex has been deliberately obstructive and has thwarted attempts to either market the property, refused to conduct viewings, or has rejected decent offers, etc etc to establish that s/he has breached the order.
Applications for leave to appeal must be made within 14 days of the order being made, so your ex is out of time.
FYI: To be able to launch an appeal against a judgement, one must be able to demonstrate that the judgment was;
Perverse - totally unfair and beyond the discretion of the judge; or
An error in law was made; or
New, important and relevant evidence has come to light which wasn't known of before and which would change the ruling.
Whether the exercise of the judge’s discretion was vitiated by a factual error
Whether the judge erred in the weight applied to evidence
Whether the judge acted beyond a reasonable exercise of discretion
Whether the judge failed to provide adequate reasons for their decision
Whether the judge denied the party natural justice in refusing to admit evidence
Even if a party could establish one or more of the above grounds this does not guarantee that s/he will be allowed to appeal or that s/he will be successful.
The process involves lodging an appeal notice within 14 days of the order, obtaining a transcript of the hearing and filing this too. S/he also need to serve the appeal documents on all parties to proceedings.
Just as a bit of advice I received, when chasing ex to get house on the market, always email, be concise and clear on what you’re asking them to do. Don’t be sucked in to an argument, start a new email each time you chase them.
I did all this. Waited 8 weeks (wished I’d done it sooner) submitted all these emails that he’d ignored with my d11. He looked very silly in court and conduct was transferred to me.