Thanks for that - it's given me a couple of things to try. I don't think it's the Splash screen issue though as users say they can't get to any more pictures whereas Android users can. These issues occur only on iPhone 6 onwards. Windows PC & Apple browsers, including Safari, iPads etc don't seem to have a problem. Just the ***** iPhone!
Unfortunately (fortunately?) I don't have an iPhone so it's hard to test.
Thank you for your advice.