Strange nighttime howling jet aircraft

A couple of weeks back a most unconventional sounding jet aircraft flew low over Westbury in Wiltshire on a track which was heading toward the Lakenheath USAF base area. It flew over at 1500 to 2000 feet around 1.30 am three times that week. What was so weird was the jet noise. It sounded like a very loud banshee howl which continued until it faded in the distance. On one day (Tuesday) it flew directly overhead (waking me again) and this time as it passed my overhead the howl changed to a muted V1 pulse-jet sound. It had military nav lights (i.e. the white tail light turned on and off but did not strobe). I would say it was flying at maybe 200kts. I would say if it was on a long-haul flight maintaining a small circle course it would have come from southern USA to pass overhead on that track.

I am a former civilian pilot and very experienced in what’s up there and I can say it was not a conventional jet engined aircraft. It was not a B2 either. My first thoughts were the new British Aerospace stealth drone that looks a bit like an F117 that surely must be test flying in UK airspace by now (it was first tested in outback Australia last year). But the sound of this drone is ‘normal’ jet from what I gather listening to the video of it on the internet.

Someone else who was awoken by this unusual aircraft came to the same conclusion it may have been something really exotic from Arazona’s secret skunkworks bases on a hypersonic, cross-pond test flight to lakenheath maybe. Aurora or something like that? Anyone know of unusual traffic into Lakenheath a week or two back in the dead of night?

Sound may be heard here: https://youtu.be/cvxDC5eNYfs