Unless your flatmate is a complete pushover I'm afraid your flatmates being annoyed is far from the be all and end all of the matter. You've taken it into your hands to get it repaired, should have either made him arrange it by phone or gone through the landlord, he does not in any legal way owe you that money unless he agreed for your to sort it out and he'd pay you the money.
He is the kind of guy who holds down a £100k+ a year job, you would think he could have worked this out himself.