ROD SCRATCHES PEEL: There had been a lot of excitement over the plans for Rod Stewart to present John Peel's show while The Great Man Of English Music And Saturday Morning Whimsy was away next week. It seems, though, Rod suddenly found out exactly whereabouts in the schedule Radio One have shoved Peel these days, and pleaded a prior arrangement. So it is, then, that next week's shows will now be presented by Underworld, Siouxse and Robert Smith - not, sadly, all at the same time. But that would be some zoo radio worth hearing. The second week of Mr. Peel's holiday will be handled on all three nights by Rob da Banks, who is not be confused with Virgin Radio's Robin Banks - same bad pun, different guy.