Bastardeaux,
Any variant of F-35 would replace Tornado exceptionally well. The radar is eye-wateringly good and the range of the -B is better than GR4 with tanks. Add in the incredible situational awareness that the sensors bring and it is an extremely potent force mix with Typhoon. Stormshadow could be carried on all three variants externally, as could Meteor.
Lowe hits the nail square on the head wrt cost and the forcing function behind the upcoming decision. Industrial work share and the return of £££ to HM Treasury will rule out any F/A-18E/F buy if it's over F-35. Too much political risk in doing otherwise. Short-termism.