Doohh ... User error - 1PPS wasn't enabled on the GPS.
The OPIO Kernel works fine w. 1-PPS
$ sudo ppstest /dev/pps0
trying PPS source "/dev/pps0"
found PPS source "/dev/pps0"
ok, found 1 source(s), now start fetching data...
source 0 - assert 1524154630.697340907, sequence: 6793 - clear 0.000000000, sequence: 0
source 0 - assert 1524154631.697261112, sequence: 6794 - clear 0.000000000, sequence: 0
source 0 - assert 1524154632.697166525, sequence: 6795 - clear 0.000000000, sequence: