while there are quite a few good 28mm Sherlocks around, for some reason I've never been convinced by the various "Doctor Watson" figures
On reflection, this is, I think, true only of Hollywood versions of the characters. If you are after Conan Doyle versions, as I am, it's the other way around. There are a lot of figures that fit Watson's description ("a middle-sized, strongly-built man -- square jaw. thick neck, moustache" -
The Adventure of Charles Augustus Milverton), but almost all of the Holmes figures have him in the deerstalker cap and cloak. No Victorian gentleman, even one as unconventional as Holmes, would have worn that get-up in town, where most of the stories are set. But figure manufacturers making Victorian gents tend to err on the side of making them portly and hairy-faced, rather than lean and hawk-like.
Two honourable exceptions to the deerstalker rule are Ironclad Miniatures, whose Holmes is in topper and frock-coat, and RAFM, who make a version in dressing-gown. But I happen not to like the former, while the latter is obviously limited to the confines of 221B Baker Street.
Ironclad Holmes:
http://www.ironcladminiatures.co.uk/shop/article_CH11/CH11.html?shop_param=cid%3D24%26aid%3DCH11%26RAFM Holmes:
http://www.rafm.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=RAF&Product_Code=RAF02913&Category_Code=COCM There's an associated Watson for each, which you might like to check out if you haven't already seen them.