there isn't one (the legally required minimum period starts at 20+ employees).
Your employer must invite you to a meeting about it in writing. they must actually have the meeting and put the outcome of the meeting in writing and they must provide you with a method of appeal.
The only stipulation for a time period when under 20 employees is "Consultation should begin as soon as reasonably practicable and before the final decision to dismiss those identified for redundancy"