Employment law is notoriously complicated, but there are some basics which apply to all employees on health and safety, wages, contracts, dismissals and redundancies which it's helpful to know.
Whether or not it is in writing, as you soon as you start working for a business, you automatically have a contract. Your employer must provide you with written terms and conditions for your job and can't change these conditions without your agreement.
Terms and conditions
Whatever your individual terms and conditions of employment, they must at least comply with legislation covering minimum pay, working hours, annual leave and statutory sick pay for qualifying employees.
Your rights as an employee
Amongst other rights, you have a right to a safe working environment.
Your employer cannot discriminate against you on the grounds of age, ethnic origin, disability, gender, marital status, sexual orientation or religion. If you are pregnant, you have other rights during your pregnancy and return to work. Adoptive parents and new fathers also have significant rights to time off work.
You also have the right to belong to a trade union.
Redundancies and dismissals
If you are made redundant your employer must follow procedures to ensure redundancies are carried out fairly and reasonably. Unfair or wrongful dismissals can be challenged in an employment tribunal. Your employer may, under exceptional circumstances, be able to dismiss you without notice for 'gross misconduct' but only by following correct procedures.
Your employer should have a written discipline and grievance policy along the lines of the Acas Code of Practice. If you feel you have been treated unfairly, you should set out your grievance in writing so your employer can deal with it appropriately.