"He then claims that our thinking is ring fenced and rationality based on entirely irrational concepts."

Of course it's ringfenced. Your starting premise is the existence of God. He's your ringfence. Without him you'd have nothing to think about. When it comes to rationality, well you set evidence aside (bad for rationality) in order to believe (not rational) in an entity who doesn't fit any of the laws of nature, who no-one has ever seen or heard, who is supposedly infinite, all-seeing and all-powerful (irrationality taken to extremes) and who can't be explained. Everything can be explained with an explanation that's infinitely inexplicable in itself. So you take this thoroughly irrational starting point and build a whole theology out of it. Oh, your theology may contain reasoning of a kind and may even reach good conclusions about why we should be good, etc. (though we heathens manage to do that too). But as soon as you start talking about God's love, God's will or God's mercy as explanations for what happens in the world, or suggest that we could pray to him for things, or use him or his mother as examples to us all, or pretend that he could do arbitrary magic on random people, not only have you become severely irrational, you've gone barking mad.