Subject rankings are tosh, ignore. RHUL does not have a placing not because it's crap but because its course is very new and there's very little data.
Russell Group means little, as does the name of the individual uni -- work hard, make good apps, and you'll have a chance to work in the City. Surrey is a good school and it appears RHUL is not too bad too. Modules will vary very little and where they do vary, you will be able to determine which you find more suitable based on your research and personal interests.
Surrey does have placement years, which is very good for employability. Beware, though, there is no guarantee they will find you an impressive firm/organisation to host you on that year. Of course, they brag about people working in commercial firms and sets, but they also list Citizens Advice on their available schemes. Were you to study at any other uni or not do the placement year, you'd be able to volunteer at CAB while studying.