Do we not have HMS Ocean patrolling off Libya? Its from this Assault ship apache helicopters will be deployed when needed. RAF fixed wing aircraft were capable to fly from Italy to Libya and back on bombing missions so there is no need for an RN fixed wing carrier.
HMS Illustrious has just finished a refit and will be relieving HMS Ocean shortly while she has a refit to 2014.
I hope you don’t seriously believe that flying aircraft from Italy is a more sensible option than using a carrier. If you do, consider how many of the hundreds (520 up to 24 May) of two-hour, 1,200 mile round trips flown by RAF aircraft from their rented facilities at Gioia del Colle to the Libyan coast (£70k per flying hour for a Typhoon plus the cost of aerial refuelling) could have been saved if we'd had carrier-borne aircraft. Then consider the fact that the Harrier AV-8Bs flying from USS Kearsarge were achieving twice the sortie rate of their land-based counterparts (link). Finally, consider the faster reaction time of aircraft based within a few minutes of the Libyan coast.
P.S. See my signature block in conjunction with this article: Harrier dump jets.