If your looking to get a telescopic ladder, you always need to check what location the ladder was built especially if you are going to be using it for industrial work. What myself and other bloggers have realized is that ladders that have been made abroad in countries like China and the Philippines don't meet the minimum safety requirement for safe workplace use, so if you are planning to buy one for your work then i highly suggest you read this http://www.techturtle.co.uk/best-telescopic-ladder/ . The website gives very good points on how to choose the right telescopic ladder without having to worry about any safety concerns.
On the other hand, if you are looking to get one for your home decoration or DIY work like myself then you should look for one that comes with a stabilizer as the website above mentioned. The one i purchased from B and Q comes with a gripped stabilizer, which not only increase the safety of the ladder but also provides a much more balanced feel than other brands. The image below shows the difference between telescopic ladders with a stabilizer and ones without one: