The temperature is set to pass 30C during this coming weekend. The following sites contain help and advice on staying safe during hot weather.

Heatwave: level two alert
The Met Office has declared a level two heatwave (8th July 2010) alert in southeast England, London and East Anglia. This means a heatwave is imminent, and there's a high chance that temperatures over the next few days could pose significant health risks.
http://www.nhs.uk/Livewell/Summerhealth/Pages/Heatwaveamberalert.aspx

Keeping safe at home during hot weather
Hot weather can cause heat exhaustion in people and animals. Also, bacteria on food and rubbish develop more quickly in the heat. Find out how to stay safe around the home in hot weather, including keeping cool and taking extra care with food and waste.
http://www.direct.gov.uk/en/HomeAndCommunity/InYourHome/KeepingSafe...

Outdoor working
When working outdoors the weather can have an effect on an individual's effectiveness and this is not readily managed using just engineering controls. In these circumstances some of the most effective ways of managing these environments is by introducing some simple administrative controls for example:
http://www.hse.gov.uk/temperature/information/outdoor.htm