My wife (impressively) cracked the iPad2 glass a cracker (by kneeling on it when the iPad was under a cover) - so much so that some fragments come away when you touch the screen. She spoke to Apple who wanted £200 to give her a refurbed unit.
She looked at a place found in google -
theipadrepair - and they seemingly offer a courier to pick up from home, send to Manchester to replace the screen and screen mount, then courier to return home... all for £90.
She's not sent this away yet, but is considering it.
As a note, the iPad has two screens, in our case the top screen is the only one broken, so if you have both broken, it will probably be more £££.