Image courtesy of John Crellin/ Floral Images
Clive Stace's New Flora of the British Isles 4th ed. lists five thymes recorded in the wild in Britain & Ireland. There's garden thyme Thymus vulgaris, with leaf margins curled backwards; lemon thyme T.x. carolipaui, with a distinct lemon scent; large thyme T. pulegioides which has a scattered distribution and can be identified by having hairs on all four angles of the lower stems; and T. serpyllum Breckland thyme, found in c22 sites in Suffolk and Norfolk. The species used in Byron's Gin is the more common wild thyme Thymus drucei, which can be identified by checking the lower part of the stems: it has hairs on two of the four faces, but the other two are hairless.