I was at Cranfield at qbout that time - cloud base was varying between 600 and 900 feet, so he would have had to have been very low! There wasn't much traffic at all - in fact the BBMF Lancaster should have been exhibiting at Bletchley Park, but the weather was no where near good enough for this.
In terms of aircraft like that, I've never seen anything so exotic at Cranfield in the last 12 months I've been going there.