Who says people don't want to buy German riesling? The limited parcel of Burg-Layer rieslings that Majestic announced yesterday morning are all but sold out. Certainly the ones I would have advised you to buy, so apologies for being away at the crucial moment.
The current trend in the wine trade seems to be for having 'flash sales' - massive reductions that are only available for very short periods. The wine merchant Slurp was offering Taittinger champagne for £21 for about half an hour earlier on today instead of their usual price of £42.95 (which of course is ridiculously over-priced).
The only way to rely on getting them is to sign up for email updates and newsletters. Which is of course exactly what retailers want you to do - and nothing wrong with that. Suspect we'll see a good deal more of it this summer.