Was in England in October and wanted to get something similar to der Spiegel, and Time and the Economist were the only things on offer. In the end I didn't buy anything. There is nothing really like der Spiegel in the UK.
I once had a subscription to Time, as it is so cheap, but after a year, when they asked me to keep the subscription up for about €25 a year or something, even that low price was not tempting: for me there was too much American news (no doubt good if you are interested in the US) and too little depth. At one point, for example, I had the New Scientist at the same time, and I noticed that the "interesting figures" section in Time seemed to be taken partly from the New Scientist, but quoting the figures completely out of context. (The New Scientist is really good btw!)
Another thing you might try, though not much like der Spiegel, is The Week, which summarises articles from various newspapers: http://www.the.week.magazine.co.uk/