mr bojangles I use Nikwax on my Brooks. You can get it from most motorcycle stores as its used on bike leathers. Comes in a tin like boot polish or as a liquid in a can. Softens and nourishes the leather while leaving a water resistant wax layer. i think it's about 6 quid a tin but'll last for ages. HTH
i used to have this stuff for doing my hiking boots, loved the smell!!