In any case they are Independent Now (with all that that entails). It's all very sad, but we are not the world's policeman any more. We should keep out of it.
The only justification for UK forces going in is humanitarian and then at the behest of the UN. Unfortunately, in the past, the 'host' country have always wanted their own forces to be included and this has sometimes led to a major clusterfkuc with unnecessary casualties. I suspect UKs own SF would refuse a combined operation on the grounds of possible causalities to themselves. It would have to be a night operation with NVG anyway and I doubt the Nigerians have them, they would have been sold off long ago.