The key piece of legislation is the Employment Rights Act 1996
Any terms and conditions that you use should be tailored to your business in order to ensure they comply with legislation and are suitable to your business.
The moment an applicant unconditionally accepts your offer of a job, a contract of employment comes into existence. The terms and conditions can be oral, written or implied, or all three.
You are under a legal duty to provide the employee with a written statement of main employment particulars within 2 months of their start date.