Vishay have the NOMCA series, 8 resistors in a surface mount package, under £4 GBP each in small quantities. These are the best bang-for-buck that I've found so far in matched resistor networks.
25ppm tempco overall, 5 ppm tempco tracking
0.1% basic tolerance, 0.05% ratio tolerance.
Stability 0.05%/1000hrs, ratio stability 0.015%/1000hrs.
All the resistors in the package are the same value but you can make a set of dividers by using parallel and series combination that are going to take advantage of the matched ratio tempco and stability ratings while being on the same substrate. Only available in 1k, 2k, 5k, 10k, 20k and 50k off the shelf, but Vishay will make them to order in any value but of course that would come at a price
Depending on your design, it might take a bit of cunning to make the particular layout of these suit your purposes. Again, depending on your design, you might get better overall performance out of these than out of say, several Vishay dedicated MPM dividers which have 2ppm ratio tracking each, but obviously wouldn't have tracking between separate packages.
If you need better stability or tracking performance than these then you are going to have to step up in price.