Very Weird IOS Bug - iPad and iPhone

This is a really weird scenario - which I hope someone may shed some light on.

I'm building a new website, and there are parts of the website that don't function at all on either my iPhone 5, or iPad 2 - (both on IOS 8.3) , yet when I try the very same thing on other peoples iPads or iPhones (various types - some identical configuration to mine), it always works perfectly (I haven't found anyone else's iPad or iPhone yet where it doesn't work).

I've tried everything, upgrading from IOS 8.1 to 8.3, shutting down, removing all cookies and history (repeatably), turning off javascript then back on etc - yet for some reason nothing changes and I cannot get the functionality to work on my iphone or ipad.

There are a number of bit of functionality that fail, but an easy one to test is:

1/. Go Here: http://test.chillisauce.co.uk/hen/london/cocktail-making_15598/

2/. Click the save button

3/. When the modal opens click the top button labelled "Yes - Make A Stag Do"

On my iPhone / iPad the button does nothing. If the code is working on your iPad / iPhone , then you will be taken to another page - if not, like me, the button does nothing.

Even if you don't know what the issue is, I'd be greatful if you could tell me if the function works for you or not.