In a flash of extraordinary inspiration, ran the command in a terminal
window from root - instead of from scite and now it seems to have worked...

root@alan-desktop:/opt/context# context --generate
MtxRun | running command: luatools --generate
LuaTools | variable SELFAUTOLOC set to /opt/context/tex/texmf-linux/bin
LuaTools | variable SELFAUTODIR set to /opt/context/tex/texmf-linux
LuaTools | variable SELFAUTOPARENT set to /opt/context/tex
LuaTools | variable TEXMFCNF set to $TEXROOT/texmf{-local,-context,}/web2c
LuaTools | loading /opt/context/tex/texmf/web2c/texmf.cnf
LuaTools | preparing configuration for /opt/context/tex/texmf/web2c
LuaTools | configuration saved in
/opt/context/tex/texmf-cache/luatex-cache/context/9d2177de8a31df158f21be632b7742b7/trees/eafbbdaaf07ecf8142ecf5e1c693b318.lua
LuaTools | configuration compiled to
/opt/context/tex/texmf-cache/luatex-cache/context/9d2177de8a31df158f21be632b7742b7/trees/eafbbdaaf07ecf8142ecf5e1c693b318.luc
LuaTools | locating list of /opt/context/tex/texmf-project
LuaTools | locating list of /opt/context/tex/texmf-fonts
LuaTools | locating list of /opt/context/tex/texmf-local
LuaTools | locating list of /opt/context/tex/texmf-linux
LuaTools | locating list of /opt/context/tex/texmf-context
LuaTools | locating list of /opt/context/tex/texmf-extra
LuaTools | locating list of /opt/context/tex/texmf
LuaTools | scanning path /opt/context/tex/texmf-linux
LuaTools | 88 files found on 9 directories with 0 uppercase remappings
LuaTools | scanning path /opt/context/tex/texmf-context
LuaTools | 1422 files found on 125 directories with 0 uppercase remappings
LuaTools | scanning path /opt/context/tex/texmf
LuaTools | 3411 files found on 112 directories with 207 uppercase remappings
LuaTools | preparing files for /opt/context/tex/texmf-context
LuaTools | files saved in
/opt/context/tex/texmf-cache/luatex-cache/context/9d2177de8a31df158f21be632b7742b7/trees/5f7b9306dcbd6a966450acbb82901a81.lua
LuaTools | files compiled to
/opt/context/tex/texmf-cache/luatex-cache/context/9d2177de8a31df158f21be632b7742b7/trees/5f7b9306dcbd6a966450acbb82901a81.luc
LuaTools | preparing files for /opt/context/tex/texmf
LuaTools | files saved in
/opt/context/tex/texmf-cache/luatex-cache/context/9d2177de8a31df158f21be632b7742b7/trees/3b345784234bafc7148851149a3f5528.lua
LuaTools | files compiled to
/opt/context/tex/texmf-cache/luatex-cache/context/9d2177de8a31df158f21be632b7742b7/trees/3b345784234bafc7148851149a3f5528.luc
LuaTools | preparing files for /opt/context/tex/texmf-linux
LuaTools | files saved in
/opt/context/tex/texmf-cache/luatex-cache/context/9d2177de8a31df158f21be632b7742b7/trees/64fe47ca42a06b0d6010805018b4cbbc.lua
LuaTools | files compiled to
/opt/context/tex/texmf-cache/luatex-cache/context/9d2177de8a31df158f21be632b7742b7/trees/64fe47ca42a06b0d6010805018b4cbbc.luc
LuaTools |
LuaTools | runtime: 0.358 seconds

MtxRun | total runtime: 0.461

root@alan-desktop:/opt/context# mtxrun --script font --reload
fontnames | identifying tree font files with suffix otf
fontnames | 161 tree files identified, 482 hash entries added, runtime 1.159
seconds
fontnames | identifying tree font files with suffix ttf
fontnames | 192 tree files identified, 559 hash entries added, runtime 2.173
seconds
fontnames | identifying tree font files with suffix ttc
fontnames | 0 tree files identified, 0 hash entries added, runtime 0.066
seconds
fontnames | identifying tree font files with suffix afm
fontnames | 69 tree files identified, 148 hash entries added, runtime 0.337
seconds
fontnames | identifying system font files with suffix otf
fontnames | 0 system files identified, 0 hash entries added, runtime 0.001
seconds
fontnames | identifying system font files with suffix ttf
fontnames | 0 system files identified, 0 hash entries added, runtime 0.000
seconds
fontnames | identifying system font files with suffix ttc
fontnames | 0 system files identified, 0 hash entries added, runtime 0.000
seconds
fontnames | identifying system font files with suffix afm
fontnames | 0 system files identified, 0 hash entries added, runtime 0.000
seconds

Alan