The UK marketing campaign begins on March the 1st. Square Enix are spending millions on advertising in the UK - specifically adverts during football matches (presumably Champions League games?) and they estimate their bus side ads will reach 75% of the population. I don't know why the UK market is important to them, it's relatively tiny I'd have thought?
They drew inspiration from Western games when designing FF13. Specifically, the Halo and Call of Duty series, because of their fast paced action. (Imo though, if you want to win over Western audiences, you make a sandbox rpg with dialogue options).
And why Leona Lewis? Well, she's the UK's 'darling'. It could have been worse. Fight, fight, fight, fight, fight for this love...
Personally, I think the marketing campaign is an attempt to offset the negative/mixed reviews Square-Enix know the game is going to get. They've invested too much time and effort in porting the game over from the PS2. There is also a review embargo in place until the day before release, which just makes me suspicious (even though I know a lot of developers pull this stunt).
I guess we'll see soon enough.