Hi Guys
I've found it varies between airlines....especially with the minimum height issue. The minimum height is a safety thing as is your reaching height so it is very dependant on the aircraft the airline operates...e.g. 757 Ceiling Stowages are obviously quite high so airlines that operate that particular aircraft will require 5'2 or a certain reaching height.
A lot of smaller airlines that operate props. etc from London City and smaller airports can require a height of only 5ft.
If your 5'1.8 - I'm fairly sure you'll be fine though even with a 5'2 height restriction. The other thing to do is test your reaching height before going to an interview so if they seem a little uncertain about your height, tell them your reaching height to sway them your way!
Best of luck in whatever airline you decide to go for!