https://www.gov.uk/aaib-reports/aaib...ior-iii-g-wavs
AAIB report now published.
Conclusion
The aircraft struck trees near the summit of Bredon Hill following flight into conditions of deteriorating visibility. The aircraft was not equipped to operate in the icing conditions forecast in cloud and so could not climb to the minimum safe altitude.
In visibility close to the limits permitted under VFR there is very little time to avoid terrain and obstacles that may be encountered and, should conditions deteriorate, flight in these circumstances presents few options for a safe outcome.
CAP 1535, published by the CAA, advises pilots that flight in the minimum conditions of cloud and visibility permitted under VFR is not necessarily safe, and describes steps that can be taken when planning the flight to mitigating the risks of flight into terrain in poor weather.