A cracked windshield isn't a big deal, though it's better to be safe than sorry to land at the nearest suitable airport (suitable being the keyword here).
There was a BA jet which lost it's windscreen 20 years ago (but safely landed at Southend). The captain had to be held by some FAs as he was sucked out of the window when the windshield blew out.
Like I said, better to be safe than sorry.
I'm surprised sleezyJet didn't charge their SLF extra money for two flights. The sooner that and Ryanair goes bankrupt, the happier I will be. What about the Ryanair/sleezyJet pilots? Well, they're not really pilots -- they're button pushers!