Hi, and Welcome to Wikipedia. However, I would suggest that you add some other references to Letts and Lonsdale Revision Guides before someone decides it is just spam or non-notable. You only cite company sites, while Wikipedia requires reliable independent sources to establish notability. You don't have to get rid of your current ones - just add some outside links that show that the product is notable. (I know that it is, but a lot of the editors are not UK based and will probably never have heard of it.) Peridon (talk) 19:17, 27 January 2010 (UTC)
I would have to second that, being US-based, I've not heard of Letts and Lonsdale, but I did find one seemingly good secondary source in the ones provided, as I mentioned on the talk page. I tried to search for some more, but since they are a publisher, the google results on book & web search are overwhelmed by materials that they have published (note that this does not in itself prove notability). The article really needs just one more link to a good secondary source (e.g. a newspaper or book they do not publish, or even a reliable independent website) for any concerns to be alleviated. Thanks! Joshua Scott (talk) 04:03, 6 February 2010 (UTC)