Below is a list of just some of the laws and guidelines everyone must adhere to when organising an event. And this does not take into account our common-law duties of care.

Yes is it very daunting. I have included it here for two reasons; one - it can be used as a reference in case you need to look anything up and two - to let you know what areas I cover and therefore how I might be able to assist you to organise your event.

Useful Acts, Regulations & Guidelines for Events OrganisersYear
Legislation - compulsory 
The Public Order Act 1986
The Regulatory Reform (Fire Safety) Order
2005
Highly Flammable Liquids and Liquefied Petroleum Gases Regulations1972
Health and Safety at Work Act1974
The Safety Representatives and Safety Committees Regulations1977
Health and Safety (First Aid) Regulations1981
The Control of Pesticides Regulations1986
Fire Safety and Safety of Places of Sport Act1987
The Health and Safety Information for Employees Regulations1989
Noise at Work Regulations1989
Electricity at Work Regulations1989
The Construction (Head Protection) Regulations1989
The Health and Safety (Information for Employees) Regulations 1989
Environment Protection Act1990
Workplace (Health, Safety and Welfare) Regulations1992
Health and Safety (Display Screen Equipment) Regulations1992
Personal Protective Equipment Regulations1992
Manual Handling Operations Regulations1992
Construction (Design and Management) Regulations1994
Reporting of Injuries, Diseases and Dangerous Occurences Regulations1995
Construction (Health Safety and Welfare) Regulations1996
Health and Safety (Safety Signs and Signals) Regulations1996
The Health and Safety (Consultation with Employees) Regulations 1996
The Confined Spaces Regulations1997
Lifting Operations and Lifting Equipment Regulations1998
Provision and Use of Work Equipment Regulations1998
Gas Safety (Installation and Use) Regulations1998
Regulatory Reform (Fire Safety) Order2005
The Management of Health and Safety at Work Regulations1999
Control of Noise at Work  Regulations 2005
Pressure Systems Safety Regulations2000
Road Traffic Act and other relevant traffic legislation
Licensing Act2003
The Fireworks Regulations2003
Civil Contingencies Act2004
The Building (Amendment) (No.3) Regulations2004
The Control of Substances Hazardous to Health (Amendment) Regulations2004
The Employers' Liability (Compulsory Insurance) (Amendment) Regulations2004
The Work at Height Regulations2005
Guidelines - strongly advised as minimum standards 
Guide to safety at sports grounds (The stationery office) 2001
The event safety guide ( HSE)1999
Fire Safety Risk Assessment (series of books - 11 in all - HM Government)2006
Fairgrounds and Amusement Parks, Guidance on safety practice - HSE)1998
Working Together on Firework Displays (HSE)1999

Note; This list is not intended to be comprehensive and legislation and guidelines may change from time to time. The author of this list does not take responsibility for any interpretations, actions or in-actions which the reader might make as a result of referring to this table.