No, it’s a fair question.
There were a fair fair few times when the Russians came south in strength during, say, a JMC and having run through all the available F4s we would scramble the SQRA Binbrook Lightnings to join a tanker and head north to intercept the next pair on the edge of the UKADR north of Saxa/Polestar and follow them in trail down towards the fleet. 90 minutes north, 90 minutes home and at least 2-3 hours in between. Never remember O2 being raised as a problem. But that was probably the same length of the average trail from home out to Akrotiri.
There was also the pleas to be able to take over the Ascension QRA role during the Falklands War (and the reputed Y missile mod so they could carry 4 sidewinders - but that’s a separate subject) - so they obviously thought they could do that leg from the UK.