After changing the rear shoes and handbrake cable I want to bleed the brakes.  I need to know what size the nut is asi don't have a spanner that small. 

I tried to use an old box bike spanner but even that was too big. 

Anyone know.  It's got to be 4 or 5mm. Can you buy a bleed spanner that small? 

I tend to go with a pair of molegrips on the small ones. Make sure you've given them a good soak in release spray first.

Thanks, I'll try that .