Graham,
Given that it was picked up going to Germany the other day displaying the same 924924 hex with call-sign GOTO FMS as it was today and you didnt see it at that specific time, I can only presume that there was no one feeding coverage of that area at that time. Looking at the Grimsby area just now on the Network shows very few aircraft with the nearest being a C172 around Scunthorpe. I was out this morning so dont know if it appeared else where before or after your noting it.
Alan