They are open to any nationality as long as they are studying at a British institution, and you need to make a case for the award to be made on academic excellence (not financial need). The application process for national awards opened on 1st December, and the deadline is 28th March 2008. There are also a number of international fellowships which you can apply for if your application is supported by the BFWG.
Finally, there is a charitable foundation associated with BFWG which does help with living expenses of final year PhDs for which separate criteria apply.
So, something to do over Christmas, then.
* I’m assuming it must be something to do with the terms of the charitable trust?