As you can see from the previous post (below), Birds 4 were in machine #93 and that is where almost all my stock has come from. Yet a single £5.40 strip is listed on eBay for £95 - as a starting price! Will the bunnies bite? Maybe, but there are probably more Birds 4 from #93 in dealers hands than from the self-service machine (#91). [You won't find that £95 one now, it's been pulled by the seller.]
Birds 3 is a different matter. This was in machine 93 at the beginning of Stampex and most people using the self-service machines (which dispensed only Machin Centenary stamps) would not have known about Birds 3 being available. Those are likely to be scarcer by far, from the Hytec machine.
And I wonder if any Wincor-Nixdorf machines in Post Offices were updated before Friday, and might have dispensed 40gr stamps? Enquiring minds need to know!