Recent auction prices of pounds 20,000 or so for E H Shepard's delightful illustrations for A A Milne's Christopher Robin books seem to put his work beyond our pocket. But outside the charmed circle of Robin, Pooh and Tigger, Shepard drawings can be picked up quite cheaply. Christie's South Kensington expects only pounds 150-pounds 250 for Shepard's pencil and watercolour drawing of a pensive Edwardian paterfamilias holding at arm's length a newspaper with a headline about the war in Russia, in its sale of original illustrations and illustrated books, Friday (11am).

The drawing displays the unmistakable Shepard casualness - he makes drawing look so easy - together with his unerring eye for the pose of individuals absorbed in thought or some mundane activity. Pretentious, perhaps, to compare him with Vermeer, but it's funny how the folk in both 17th century Delft and Hundred Acre Wood seem to be up to nothing much, apart from savouring the poignancy of he moment. There are seven other Shepard drawings in the sale, with estimates ranging from pounds 200 to pounds 600.

Less familiar images of William Heath Robinson are likely to be cheaper, too. He is chiefly sought after for his drawings of outrageous contraptions - such as the one for inserting peas into the mouth - which sell for pounds 1,500- pounds 2,000, especially in colour. Two unmechanical but equally charming monochrome wash drawings of his are estimated at only pounds 600-pounds 900 in the sale. One shows four old men disguising their bald pates as eggs in an attempt to lure wild turkeys to their nest, the other a gravity-defying edelweiss gatherer supported on a cliff face by a turkey fledgling.

Still funny today? A seaside postcard original by the saucy Donald McGill has a lower estimate than usual - pounds 200-pounds 400 - because in the last sale, in December, nobody found his cartoon of "The chubby boy", estimated pounds 250- pounds 350, funny enough to buy. Someone did bid pounds 540, over pounds 300-pounds 500 estimate, for one captioned "Oh, Mr Murgatroyd, how bare-faced of you". The pencil- and-watercolour in this sale has a fat, buck-toothed countryman with carpet bag eyeing two well-endowed London lasses, with the caption "No wonder they call this the Metropolis".

Next Saturday (1pm), Bonhams holds its ninth sale of 20th century design - and the first since Sotheby's and Christie's South Kensington muscled in on the market last month (selling 69 and 86 per cent respectively). Bonhams has out-trendied them both by emphasising design rather than decorative arts. The result is a sale so surreal that you can flip through the catalogue hardly knowing whether you are looking at chairs or table lamps. There is a deliberate absence of illustrations of boring old Eames reclining chairs and no sign of other staple 20th century fare such as the Italian "Jo" baseball-glove sofa.

Among the new-to-auction lots are the Italian Studio 65's 1971 Capitello chair, in the shape of an Ionic capital, and - Italian again - a giant pink polyurethane foot made by Gaetano Pesce in 1969, "Up 7, il Piede", at pounds 4,000-pounds 5,000. That estimate should be steep enough to deter the dowdy, down-dressing young voyeurs who packed South Ken's sale but were too clueless to snap up the few lots estimated at less than studio door prices. There are no in-production lots in this sale. Honest, guv.

Single-owner collections often present buyers with a once-only choice of dozens of something previously uncommon at auction - and at a price lower than single specimens might attract. For example, Christie's South Kensington's sale of scientific instruments, Thursday (2pm) has 30 pocket- sized coin-weighing balances from the 17th-19th centuries when coin-clipping was rife, ranging in estimate from pounds 300-pounds 400 to pounds 1,000-pounds 1,200. An 18th century German example est pounds 700-pounds 1,100 has a lion-shaped knob to hoist the pair of brass pans and a set of weights representing the ecu, ducat, noaille and guine.

John Windsor