score:8
Yes, based on other cases, compensation is due in this situation under EU261.
The relevant portion of the EU261 regulations state:
(14) As under the Montreal Convention, obligations on operating air carriers should be limited or excluded in cases where an event has been caused by extraordinary circumstances which could not have been avoided even if all reasonable measures had been taken. Such circumstances may, in particular, occur in cases of political instability, meteorological conditions incompatible with the operation of the flight concerned, security risks, unexpected flight safety shortcomings and strikes that affect the operation of an operating air carrier.
As you state, other flights were operating without issue on the route you were flying, so the meteorological conditions the airline are relying on for their case is not related to your flight.
In the UK, this has been interpreted by the British courts as not applying to delays caused by events elsewhere, so airlines cannot use issues such as scheduling problems caused by weather elsewhere to refuse you compensation.
In 2013, easyJet was ordered to pay compensation in such a situation, and in 2016 a passenger received compensation from Ryanair under similar situations.
In 2016 Monarch was ordered to pay compensation by a Judge who ruled that adverse weather conditions were to be anticipated by an airline in its planning.