People don't know about ISE, but that doesn't make it a bad course.
On the contrary, we are a small community within the Imperial community. The 4 years of ISE (4*30 = 120 people), and some lecturers who specifically take care of us haha.
On a more serious note, ISE is an awesome course, especially if you get in now, they've just gone through re-arranging courses in different years so you get the very best from the beginning (unlike us who had to do Analogue in first year ugh).
If you tell most people at Imperial, "I'm doing ISE", people will first go "what is it", and once you explain they'll go "oh yeah, I know someone who does that". Seems annoying at first, but you realise that in fact, in spite of the small intake, ISE students are EVERYWHERE! We RULE Imperial :P
Jokes aside, we have a great course, broader than both EEE and Computing while still enabling you to go into more detail in either subject in the future. Turns out many ISE people also have "social" positions at Imperial. Quite a few of us work at the Union, are Hall Seniors, Presidents of Societies, are involved in humanitarian projects.
I'm not saying it's not the case of other students, but there is (at least in my year), this sort of spirit between us, that pushes us to take initiatives, in a way, to "do stuff", and I think it's very important.
Conclusion: great course, great opportunities to take initiatives, do extra-curricular stuff and amazing coursemates (I have to say, as much as I bitch about them most of the time, I never have more fun than when I'm with my course mates). Go for it.
Oh, and for finance, don't worry, ISE is all about computing and engineering, so banks will be chasing after you. And you can even do a 3-year BEng and do MSc Finance anywhere you want afterwards! (it doesn't matter if you apply for BEng or MEng, you get to choose at the beginning of your 3rd year).