The FI has great resources of fish and looks as if it has some oil - not on the scale of the N Sea sbut yes, resources.
But no-way are they critical to the UK - we fought the war because the people were taken over by a military dictatorship and we were right to do so. I don't think there is any real chance of a repeat in the immediate future (say 5-10 years) but it doesn't cost a great deal to keep a presence there ( great for training) except maybe the River Class boats
And we build them to keep Scots yards open rather than for fighting anyone serious -also the Fi do make a contribution - in $$ which will go up when the oil flow starts