The Spice Girls are pocketing "a million quid each" (we imagine there's some journalistic hyperbole invested in that figure) for advertising soulless storeborg chain Tesco:
"Should find it funny" is a bit of an odd phrasing, isn't it? Like "might be idly amused", it doesn't exactly speak of much confidence in their abilities.
Mind you, the Jane Horrocks ads weren't famous people "sending themsleves up", as they were all playing characters, weren't they?
Still, viewers should find it funny. Especially those scraping together enough to get a cart full of Value Brand groceries. They'll be gurgling with delight at helping Beckham bank a few more thousand quid.