At £400 with its 18-55mm kit lens, the Sony NEX-F3 is currently the cheapest of the three models, with the Samsung NX1000 and Nikon J2 priced at £480 and £500 respectively for their own kit options. Given the resolution of its screen, focusing performance and lack of image stabilisation over the others, the NX1000 may appear somewhat overpriced, although the premium is perhaps justified in part by the higher-resolution sensor and inclusion of wireless functionality.
Although the Nikon J2 is also considerably more expensive than the Sony F3, its similarity to its J1 predecessor means that it's well worth considering that older model, particularly as it can now be found for around £160 less than the J2. True, you'd miss out on the improved display, metallic body and the Creative Mode, but considering the significant saving some will no doubt be happy to make those sacrifices.
Although it's not quite the cheapest CSC available - Panasonic's G3 and Olympus's EPL-3 both being cheaper yet still credible competitors - the Sony F3 appears as the bargain option out of the three. Anyone interested would also be advised to also consider its NEX-5N sibling which is only around £20 dearer at present, as it has the advantage of a faster burst rate, wider ISO range and, if indeed it's considered to be an advantage, touchscreen operation. If wireless functionality is of interest, Sony's latest wireless-enabled NEX-5R and NEX-6 models are also worth considering.