What is the best brand of mandolin please

It depends on your budget. Bron Couke and Benriner are very good, however, they are very very expensive and most domestic cookware stores do not sell them. They are available commercially and I have had the odd customer wanting them. The Mastrad mandoline is a very good one, it is French and has eight different blades for various tasks with adjustable thickness. Zyliss also do a good one.
http://www.dailymotion.com/video/xiqumg_video-demonstration-professionnal-mandoline-bron-coucke_lifestyle http://www.youtube.com/watch!v=Dt5KiL-3S0Y

Mine is Benriner brand made in Japan - the best blade, so they say,"for household and professional use".

Edited to add: http://benriner.com/bought in NYC