The OS map is driven by OS themselves, I'm trialling it as part of the OpenSpace project along with many others. Its based on the OpenLayers API. Bill Chadwick who does the Wheresthepath site is the master of this type of scripting.
I'm totally Mac based and I have been playing with the OS Openspace API and the iPhone, sadly the Safari browser used by the iPhone is a cut down version of the Mac one and will not allow vectored browsing but the iPhone version still comes up OK apart from not being able to scroll etc. It can also be viewed in a normal browser Mac or PC. It lives here
http://www.toadstone/OS/iphone OS are also doing a gazetteer which is awesome. Again I did it for the iPhone but you can view it in a normal PC browser.
You can try it here
http://www.toadstone.com/OS/iphonegaz It will give results for any entry on an standard OS map, just put in Nostell and press find me a map, it should return 2 results, just click on the Priory and hey presto map appears.
Hours of fun.
PS the reason the map is small and to one side is because the page is written for the iPhone, if you haven't already sussed that out.