I spoke to Simon and Guy at Opie oils the other day and ordered 25liters of Silkolene Pro S 10/50 for my Sapph.

Wierd stuff, it's purple when it's new!

Very imformative, quick delivery and I'm very happy with the service I recieved from them.

Recomended!

And it was not dear, in fact it worked out to £6 per liter.