Believe the US call this sort of rumour Horsesh*t!
I don't think the Govt would support the RN buying F-18F at all and here's why:
Dr Fox has gone on record saying that the SDSR will be looking for a UK Fast Air solution for '2020 and beyond'. Sadly that will rule out an F-18F unless we decide to replace Eurofighter with it - the platform is still a 4th Gen fighter with a slightly better AESA radar, so not exactly a quantum leap forward in technology for the money you could spend elsewhere.
HMG are going to be making swathing cuts to the UK FJ inventory that will help pay for a platform that will have contemporary, as well as future, growth; i.e. the most appropriate, affordable, variant of F-35 to match whatever SDSR decides is our 'role' in the modern World.
My personal view is that GR4 is going to go the way of the Jaguar (and perhaps the Harrier may also too) however, a Govt that wants to support Afghanistan until 2015 can still continue to do it with Harrier at a much-reduced cost to the UK tax payer whilst still providing top notch CAS for the guys and girls in the thick of it on the deck.
Rafale is pants quite frankly - and you think that the French would sell you the same version as theirs? No, seriously, non.