There are a number of immediate issues to consider with the data.
The most significant of these problems are the first and last ones. Changing the format of data can encompass both the on-disk format (e.g. the file type) and the structure – the way that the data are laid out. In general, the process of converting from an address to a precise georeference is known as geocoding. We already have a georeference for our data – the OS National Grid easting and northing – but this is not yet in the correct format that we want to use.
We will look at formatting on the next page. The process of editing data such into a usable form (or at least, into the JSON Javascript array format that we wish to use) is fairly painful. Here's a version of the data that has already had most of the processing applied to it. You are free to use this version. Note however, that this data file will still need some work – it contains some incomplete entries (for example, with missing co-ordinates), that you will need to find and decide what to do with. That said, it may be useful to read the format section in order to understand the lengthy process that was followed to get the data into the required form. As stated previously, it is a common occurrence to have some data that you wish to map, but that have a structure that it not very close to the structure that you require.