I want to split my account as I wish to separate "The Spanish Legacy of Food" hubs and put them in their own account so that advertising is more specialised for them. Is this possible, and if so what options do I have besides re-publishing them?
Also if I was to do this, would the advertising be more specialised if it was all about the same thing?
Your only option is to start a second account and do a whole manual delete and republish routine.
Remember that advertising is all based on who is viewing the Hub, so what you see might be different from what someone else in another city would see. And much of it is based on the viewer's own search activity. In short, it would be hard to say and most likely it wouldn't be all that different from the ads it gets now.