It is clear that on the question of God's existence Dawkins comes down firmly on the side of certainty. His dismissal of Pascal's wager (which is that, given the uncertainty, one has everything to gain and nothing to lose by belief in God) is a stark indication of his commitment to certainty.
I haven't read Dawkins' book, so I guess it's possible that the reason he dismisses Pascal's Wager is because he thinks it certain that God does not exist. But surely a far more likely reason is that Pascal's Wager is, very obviously, logically invalid. Even "given the uncertainty," it simply doesn't follow that "one has everything to gain and nothing to lose by belief in God". As I point out here, Pascal's Wager fails because it's possible that God might punish believers and reward atheists. So it's possible to "lose" by believing in God after all. Obviously. Really, there's nothing more to do here but smack your forehead a few times. The argument really is that bad. So the only thing "indicated" by one's dismissal of it is the possession of a minimal level of logical discernment. A pity Unwin shows no such indication.
As for Dawkins' assertion that moral behaviour for believers is simply "sucking up to God", or that morality doesn't need faith, I feel that such observations miss the more fundamental question of why we have moral or aesthetic values at all - such as the ones by which Dawkins, myself and others venerate rational analysis. This is among the questions that, to my knowledge, no science is on the verge of answering compellingly.
There are two quite distinct questions in this vicinity. One is merely a question about contingent human thought and behaviour ("why do we care about stuff?"), and thus to be answered by psychology, obviously. This appears to be the question Unwin is asking, so it's quite incredible that he doubts it has a scientific answer.
The second possible question is more general, asking why there is real value in the world at all, if indeed there is. ("Why is stuff worth caring about?") This is a deeply philosophical question, of course. And since religion has no more place* in philosophy than it does in science, I don't see that this option is any friendlier to Unwin.**
* = In either case, religion may be a topic for investigation, of course. But religious methodologies -- e.g. revelation, and clinging to otherwise indefensible views by appeal to "faith" -- are no help in conducting science or philosophy.
** = (Really, it pisses me off no end when people stupidly assume that just because a question goes beyond the scope of science, it's therefore a matter to be settled by religious dogma. Quite how they imagine licensing the step from scientific ignorance to accepting the random guess of your local priest, I just don't know.)