What is it you're thinking of buying, if you don't mind me asking ?
If it's something like a motherboard it will probably just be damaged box/missing cables. I bought a B-Grade HDD over a year ago and it still works fine to this day, saved myself around £25 on that.
If the product doesn't work OcUK will refund it anyway so if it's a significant saving you may aswell go ahead with it.
Why don't you just get this one? It's cheaper and brand new.
The current site doesn't work at all with the B-Grade/Clearance section any more. There's no quick and easy way of navigating through the B-Grade sections.
The navigation used to let you go into components, but it now just takes you straight into the "normal" components. It's just a massive PITA to find anything now.