loud and low quite unusual at 00:38 we get helicopters sometimes very late this wasnt one it woke both me and mrs up and made us look out of the window
I live under the final approach for RAF Mildenhall, at the moment we get two and occasionally three Ospreys coming in almost every night usually around 11pm . Probably the same ones that you mention.
KNIFE72, KNIFE73 and KNIFE74 on the online radar sites that show military stuff.