I wired in a rugby MSF clock into my raspberry pi, and wrote my own software to interface it to NTP.
Unfortunately I wrote it in winter when they were transmitting approximately GMT. Now its summer time and so they are transmitting British Summer Time not GMT; this is indicated by a bit in the time message. That I ignored. Oops.
Bed time project today was to add that in. Now I've got my stratum 1 server back.