Boslandew,
My first point was that an engine runaway up is a difficult emergency to deal with, even in good weather conditions. When operating in the minimum weather conditions allowed under RAF SH rules, this would be more difficult to deal with. Although the MK1 simulator allowed the emergency to be practiced, I don't know about the MK2. Did the crew have the chance to practice this type of fault in a MK2 simulator? I don't know the answer.
Secondly, I don't think the crew had any option to change the weather minima regulations they flew in just because this was an untried (and untrusted) aircraft variant. A management issue.
My own opinion is that the aircraft should not have been used for this flight or any other until any servicability uncertainties had been completely resolved. The pax should have been on an IFR capable aircraft; any other transport (civvy if necessary) should have been used in preference to one that had been grounded by the test pilot organisation the day before! I feel that egos / politics of upper management were a very major factor in the causal chain of this tragedy.
BTW, the Puma sim also had this emergency programmed in, but this was/still is a non-DECU aircraft. The diagnosis and handling of a DECU emergency can be more difficult than a non-DECU equipped one, especially when the failure mode is not forseen by the manufacturer, as was the one I personally experienced and was referring to.