The fantasy segments in PR are really interesting just for the light they throw on the characters playing the characters (so to speak). You get to see Nicola wishing she wasn't involved and being as colourless as possible, Ginty making up to Patrick via this rather homoerotic friendship between their characters (pre-empting the Rosina stuff), Peter dealing with his own fears of cowardice via the torture scene etc etc. You also get to see AF writing a very different kind of fiction, too, and I think it makes the 'real life' Christmas segments of the book more compelling by contrast, if you can see why, say, Ginty is unwilling even to spare an afternoon to go shopping for a non-awful dress.