Pieceing together what I am hearing, GEYES had been out on an environmental survey and was on approach having been handed over form RAD to TWR, then the incident happened further down the approach. Radar was fully servicable and manned at the time.
But having worked RAD at Cov (on the set up they still have), I can tell you that it's not easy doing radar in Class G airspace, especially primary radar. After you transfer any IFR inbound to TWR, you can only watch the surrounding area and hope that other airspace users will try to avoid the instrument approach path. You can only pass traffic info to the TWR to pass onto inbounds, there's nothing else you can do.
Of the two ATCOs on duty yesterday, I think they were both there back in 1994 when the 737 went into Willenhall Wood.