Thanks for the ideas guys.
I had considered finding my own cable and connecting the sockets myself, but guess what - I had trouble finding the cable too! Everything seems to be sold as 'audio cable' or some other application. How do I know the cable I'm buying is suitable for DC? And can you...
I recently bought this item from eBay. Notice it includes an extension line:
http://www.ebay.co.uk/itm/12V-2A-Power-Supply-Adapter-100V-220V-Extenstion-Line-/250874668278?pt=UK_Sound_Vision_Other&hash=item3a694ba4f6
Now I'm going to supply power in a different way... but I'd still like to...