Ended up getting this a few days ago:
http://www.ebay.co.uk/itm/Photo-Studio-Kit-Table-tent-80cm-softbox-2x-85w-Light-/160423281292?pt=UK_Photography_StudioEquipment_RL&hash=item2559f9028c#ht_3113wt_1139Still waiting for it to turn up as it's an HK special, but will let you know how I get on once it arrives. In the past I've tried using black or white card but I've never found any that is right, it's either too gloss or too grainy.