All laptop brands will have different levels of quality. Even a brands with a good reputations for quality like Asus, Sony and Toshiba have budget, entry level models with reduced quality to same costs and compete at in the value segment.
Among the major OEMs like Dell, HP, Lenovo the business class laptops have a reputation for increased durability, reliability and longevity. Which makes sense since you expect a business class laptop to go through a heavier duty cycle than a consumer/home laptop.
At your budget range of around £400 there isn't going to be a huge difference in over all quality between the various brands.
Whatever brand of laptop you decide to buy(Doesn't really matter which one you pick because there are only a few companies that make laptop mother boards so they all are similar, your just paying for a name). Anyway buy it from the companies site. You have a better chance of getting the features that your interested in having rather than some generic built laptop for the masses. The warranty is better and the quality will be better.