A new article on using the C-130J for MPA. Notes that everyone seems to have concluded that P-8 is the answer for the UK, but with with the planned drawdown of the J, thre will be some airframes around.....And roll-on, roll-off pallets allows for repurposing.
Note the comments on torpedos, which they say could be fitted.
Paris Air Show 2015: Lockheed Martin says maritime C-130 offering for UK has international potential - IHS Jane's 360