Hello Stu,
The draught is that of the sim, and is also consistent with VLCCs, look for instance at http://www.pacificenergypier400.com/index2.php?id=16 .
Also, I supposed too that the Needles channel is not the best route to Southampton for deep draught ships.
Not knowing much of British harbours (but Weymouth & Portland, Dover), the only place I knew was Bantry Bay in Ireland. Nice place, behind Whiddy Is, Glengariff "cove"(?), Bear Is with a French sailing school, and although there was no tanker in sight, it was surely deep enough. Is there a similar place in the UK?
Regards,
Luc
Edit: Thanks and sorry Kevinmcg_ships, having missed Hunterston (bulk terminal?), found Ineos (?) Finnart oil tanker terminal in Loch Long. (pictures http://www.flickr.com/photos/alancaldwell/1139405205/ )