I was recently flying in the vicinity of Brize / Fairford. There is a danger area D218A SFC-FL75 activated by NOTAM. I checked NOTAMs before flying and there was no activation NOTAM in place. When flying I saw the message pop up "Entering Danger Area D218A" and a feeling of dread washed over me. I thought I'd busted the Danger Area, and the NOTAM had become active during my flight. I was non radio so couldn't check. Spent the rest of the flight worried! On landing I confirmed there was no active Danger Area. So, the question is, can these warnings be suppressed if the Danger Area is not active? I see the same for Fairford MATZ, but I'm less concerned about that, as legally I could enter a MATZ.