crutschow, it was that Instructable that got me from wistful to serious in the first place! Then I started looking at commercial bench meters and thought, why can't I go the extra digit?
Vishay do 0.01% and 0.001% resistors - I've already had a couple of used 0.01% ones off eBay about £3 each - new they cost twice that, so that makes an expensive divider! Looking at the data sheets, I see whilst the MAX110 is specified as 14 bit, the MAX1498 is specified as 20,000 count. for 5 1/2 digits I think I'd need 200,000 count or 19 bits. OK so 4 1/4 digits is much easier...
Actually, thinking about it, since my intention is that this thing is only worth building if I can include a lot of extra functionality, and I want to make it be microcontroller controlled, is there a reason I can't do a low-count/high count and add them together? Or am just out with the fairies now?