The Valiant crash to which you refer was probably the one at Spanhoe, which is documented elsewhere on this site.
There was a brand new Victor that went in after take-off about 3 1/2 miles east north east of Wittering on 20 Mar 63 but there were other aircraft as well. I guess this crash is 180 degrees out from your recollection
Please can you refine the timescale here. What year were you born and hence what is the likely timescale for this accident, if you were visiting in the '70s. The Victor at Cottesmore on 14 Jun 62 is also not a contender but we could be looking at a completely different era. For example, the USAAF had bases in this area and my maps show clearings in Collyweston Great Wood but nothing in Bedford Purlieus. Kings Cliffe, Ketton and North Luffenham could all have contributed to an accident in this area, so are you certain it was a Wittering aircraft, rther than somebody elses?
Old Duffer