I was actually there on Saturday and was absolutely 100% convinced it wasn't it. I even showed my friend this forum thread and we both agreed it couldn't be the same pub!
Maybe we should try a more systematic approach. Everyone in this thread should be allocated a few square miles of Sussex, 'investigate' every pub in their patch and report back.
Surely the MG owner must have some idea roughly whereabouts in Sussex it was? Even East or West would help. You said he was from Eastbourne but thought the pub was in Arundel. Why did he think that? Could it actually be in Hampshire?