Best USB2 External Enclosure For NEC 3540?

I currently have the Ebuyer home brand External enclosure for my NEC Drive. It is though not allowing burns of over 6x.

I would like to burn faster than this in an external enclosure with this drive.

Could you possibly please recommend a brand of External Enclosures and where to buy it that allows good fast steady burning through USB2. (i know firewire may be better but i only have USB2).

So could someone possibly provide a link to a store in the UK selling a good model of external Enclosure. As i am not too versed on the in’s and out’s of these hardwares.

Thanks
Anthony