Quick update: After advice on this thread, I ordered these tags from Shearwell. We even managed to get our farm name printed on the wee bubble bit on the end, so that's a nice touch.

They arrived quickly, but there was a mixup with the order, and half of them arrived with the wrong flock number on them (it was an easy mistake to make, and I can see how it happened). Anyhow, Shearwells apologized profusely, told me to send back the wrong ones and they would issue me with new ones. These arrived yesterday complete with a small envelope of coins to compensate me for my postage.
I always think that the measure of a company is how it manages when things go wrong, so I'm pleased to report that Shearwells passed this test with flying colours. The tags went in very easily and look very secure, so I'm happy and will definitely be sticking with this type in future

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