The Chinese keep the value of their currency low. This means cheaper stuff for us. Why should this be a bad thing for Britain (or the USA, or others)? The argument goes that because Chinese exports are so cheap, other countries are at a competitive disadvantage on the world market.
To me it seems a bit like saying that it would be better if Waitrose charged you and the world more for lettuce so your kid had a better chance of making a living as a farmer. Why not enjoy the cheap lettuce, pocket the savings and encourage your kid to do something else for a living?