Rob,
Just tried it with 5.5.24 and it seems to work ok.
at+cgmr
RHL85xx.5.5.24.0.201704131036.x6250_4
OK
at+gpsconf?
+GPSCONF: 0,0
+GPSCONF: 1,2
+GPSCONF: 10,1
+GPSCONF: 11,200,200
OK
at+gpsconf=10,1
OK
at+gpsconf=10,2
OK
at+gpsconf?
+GPSCONF: 0,0
+GPSCONF: 1,2
+GPSCONF: 10,2
+GPSCONF: 11,200,200
OK
Regards
Matt