My Genesis Croix de Fer

FWIW, the 725 version won't be that much faster/lighter.

To be honest, it felt a little bit dull, 520 is pretty basic stuff, the 725 is worth going for a springier ride*.

*laterally stiff, vertically bouncy, whatever it is.

Am I right thinking it comes with Sora?

Modern groupset nowadays are capable up to 32t, the Shimano Claris budget derailleur are designed to go up to 32t for example.

the Deore is useful if you want to go more than 32t, which is why I put it on JB's CdF, except I end up sticking with the 32t.

I'd look at this, it's basically the same for less:
http://www.wiggle.co.uk/verenti-substance-sora-2014-free-lifeline-basic-kit/

Great value but got a really small headtube for the size (Genesis' equative is 15-20mm longer).