The Great Britain Sasakawa Foundation have PhD Travel/research grants to go to Japan and these can be applied for by students that are also in receipt of a GBSF award if it is outside that academic year of the GBSF award. There are three opportunities in the grant rounds for students to apply: 31 March, 15 September, and 15 December.
More details here http://www.gbsf.org.uk/grants/overview/
