Id recommend doing a couple things
1) going on open days or other events at both universities as it sometimes helps to see the campus and feel what its like to be there
2) compare prices, London for example is very expensive, so you may need to figure out your maintenance loan cover and how far this would stretch at either university
3) loads of websites now compare student satisfaction across different courses and different universities so it may be worth checking that score and seeing how others who have studied there score it
4) look at the modules they both offer, one might cover the area of history you are interested in more than the other
Hope this helps!