Go to GSF chap. £15 and are easy to fit...well, sort of, once i'd broken the inner arm clip on the pax side but drivers side was a doddle once know how.
Just lift wiper off the screen (stating obvious there - sorry)
Press down on the clip in centre - this will pop up slightly at about a 45 deg angle.
Slide out blade - New one on, reverse all - job done!