Short answer: Apply at least 10 working days before settlement. Allow 15-20 to be safe.
You must apply at least 10 working days before settlement. But allow 15-20 to be safe. The money goes to your lawyer, not you. If you miss the deadline, you might need to delay settlement or find the money elsewhere. Banks will not wait.
Settlement Date: 15 August
Apply By: 1 August (10 working days)
Safe Apply By: 25 July (15 working days)
Result If Late: Settlement delayed or alternative funds needed