Alexander Carpet Cleaning did a great job in our one bedroom flat. They came and gave us a quote and then cleaned the carpets to a very high standard. They're based in SE1 and I'd be happy to recommend them. Their web address is www.alexandercarpetcleaning.co/ (it looks to me as though there should be .uk on the end, but if you copy and paste into your search engine their website comes up). Hope that helps.