In fact the email to the mediator could even be a bit more - maybe something like
"Following my MIAM appointment with you on x date, it was intended that mediation would progress. However circumstances have changed and I now need to apply to court urgently. I would be grateful if you could send me the mediation sign off, by email, as soon as possible please."
"Following my MIAM appointment with you on x date, it was intended that mediation would progress. However circumstances have changed and I now need to apply to court urgently. I would be grateful if you could send me the mediation sign off, by email, as soon as possible please."