This.
The UK government made them available sometime in the last 6 months or so...
They have not released the Landranger or Explorer maps which are the most useful.
However, you can sign up for the OpenSpaces API then you will get a key you can use to access them for your website. Probably it is not within the licence agreement but you could use these tiles in Mappero after applying some transform (from OSGB grid alignment to Lat/Long). I have seen this done using a proxy but it would be nicer to add OSGB support to Mappero natively.
