I would bimble on through in my aircraft (three axis microlight, Rotax with electronic ignition), without worrying. I have not been through there by air yet but I have transited the HIRTA just to the east of Portsmouth many times. I have yet to experience any equipment malfunctions in the area while using Acom radio, ANR headsets or Skymap GPS and either 2 stroke or 4 stroke Rotax'.
If the radiation was as bad for humans as some have suggested there would be a lot of fried walkers about, the Lyke Wake Walk passes through the area and is in line of sight for some distance. Also, I have been to the NYMR for the wartime weekend (October) many times and most years there has been a flying display (aerobatics) at Grosmont, Goathland or Newtondale performed by a Tiger Moth. Also, a chap in Goathland keeps a helicopter at his house, he must fly in the zone regularly.
Enjoy.
Rans6....