Nunnis 17.2.1799 at Holcroft's / Nunnick 17.3.1799 there / 16.6.1801 call on Nunnick
Nunnis being a rare to nonexistent surname was probably Godwin's mistake for Nunnick on first hearing

Work notes: 
name on familysearch mostly Lancs particularly Colne, the only examples i could find nearer London - Henrty Nunnick bur 9.6.1804 St Margaret Canterbury, Ann Nunnick bur there 4.8.1804 / Thos Nunnick = 15.1.1771 Trinity, Ely Sarah Warwick, bur 31.7.1795 Chatteris Ely / Thos Nunnick = 21.4.1800 Lenton, Notts Hannah Clark their dau Hannah bapt 4.7.1813 Clewer, Bucks / Wm nunnick = 16.11.1756 St Giles Cripplegate London Elizabeth Mucklason their son Thos bapt 7.3.1758 St Botolph Bishopsgate / Ann Nunwick bur 1785 London noncomformist