If the Vulcan now has dispensation to fly under IFR, then fine. Consider now VFR only:
From those METARS, at no stage was the visibility below 5km - so no problem there either.
However, outside CAS (e.g. at Uffington), an aircraft flying under VFR below FL100 must adhere to the requirements of Article 28(2) of the Air Navigation Order. But under Article 28(4) of the ANO, these conditions are eased if the aircraft is not a helicopter and:
(a) flies at or below 3,000 feet above mean sea level;
(b) flies at a speed which, according to its air speed indicator, is 140 knots or less;
(c) remains clear of cloud with the surface in sight; and
(d) is in a flight visibility of at least 1,500 metres.
Provided that the IAS remained less at than 140 KIAS, the METARS indicate that VFR flight would be lawful. Now, some will ask whether the Vulcan can fly at 140KIAS....
Below 130000 lb AUW, Approach Speed is 140 KIAS and below 120000 it is 135 KIAS. The last operational Vulcan trip I flew in 1980 included a minimum landing weight of 119400 lb. Remember - 558 is much, much lighter than an RAF aircraft, having a ZFW of only 100000 lb and a minimum landing weight of about 107000 lb - some 12400 lb less than the last Vulcan I flew in 1980.
With the low fuel state needed for the flight, it would certainly have been possible to remain below 140 KIAS below an overcast cloudbase such as those quoted in the METAR, given a pilot with the skills of any VTTS pilot.
I think it's entirely reasonable for M-o-t-F to have queried the wisdom of such a flight; he certainly doesn't deserve the rude comments thrown at him by some of you lot who should know better.
I consider that no rules would have been broken; however, it would have required a skilled crew to have remained within VFR limits
and to observe the requirements of Rule 5. Whether it was wise to have flown in such conditions is a matter of personal conjecture.