Wow! You'll have completed the challenge by the end of September!
I went a bit mad as I found 27 on a roadwork sign that will disappear soon, and wanted to get it before it did. I'll slow down now, though I can get 32, 33 and 34 commuting tomorrow.
I've got every number bar 36 and 41 earmarked, can't find them for love nor money, so may have to revert to the bus signs for those two.