With some help, I now come up with 15 folks...which include 2 with dual NZ/British citizenship-- Kevin DuPuy and Paul Smith. Kevin has since returned to the UK, but Paul is a resident of New Zealand. Note that Paul Smith is the only person on this list with 2 winters...
I still suspect that there may have been one or two more, especially for SPASE, which originally had extensive British involvement.
Joshua Veitch-Michaelis IceCube U. of Wisconsin 2021 Julien Naylor Physician UTMB 2020 Paul Smith Plumber/UT RPSC FEMC 2010, 2008, 2007 Ross Williamson SPT U. of Chicago 2009 Stephen Padin SPT U. of Chicago 2007 Kevin DuPuy sheet metal worker RPSC FEMC 2004 Simon Balm AST/RO SAO* 1996 Simon Hart AMANDA U. of Wisconsin 1996 Andrew Jones astrophysics NOAO** 1995 Andy Coulthard SPASE Leeds/Wisconsin 1993 Peter Surrey SPASE Leeds/Wisconsin 1992 John K Chan SPASE U. of Leeds 1991 Michael Finnemore SPASE U. of Delaware 1990 Alistair Walker SPASE U. of Delaware 1989 Nigel Smith SPASE U. of Delaware 1988 *(Smithsonian Astrophysical Observatory) **(National Optical Astronomy Observatory)