forget,
Two likely options for a protracted incident:
If there's an airfield with Jet A1 within easy striking distance, it will be opened for the SAR helos by the ARCC who can generally count on the goodwill of the airfield operator (for instance Barrow/Walney, who turned out at midnight in February when there were four thirsty Sea Kings attending the Grayrigg train crash).
If there's not a suitable airfield, a bowser will be dispatched from the nearest (usually military) airfield and positioned somewhere suitable - this is not uncommon in the more remote parts of the UK, eg the Boulmer bowser at Harbottle during the fire-bucketing at Easter this year, and the Kinloss bowser on the Inverness-Ullapool road, fuelling the Lossie and Stornoway helos, after the Stornoway mail aircraft crash a couple of years back. These are just two incidents I was involved in which I can recall off the top of my head - there must be plenty of others.
TOTD