There are two space modules at Bristol are Space Systems and Advanced Space Systems. All in all, they are pretty basic (in terms of difficulty but do cover a lot. But you should be able to do a space design project for your major design project and that may have ties with Astrium.
I had a look at the Southampton modules and they don't look like anything THAT great only in 4th year you get to specialize and some of those are options. Spacecraft Propulsion is covered in the Bristol units a fair bit, as is instrumentation. For the structural design/ engineering design ones from Southampton, they are covered a little, but if you do the space project in bristol and focus on the structures part, you'll obviously cover them in detail too.
My advice is to think very carefully about what you want to do. At present, I would expect that any aeronautical engineering degree will put you in good stead to get into the space industry. Have you also thought about doing Physics BEng (an choosing space related units) and then doing an MSc in Spacecraft design (if that is possible)? Finally, I'd say that all of those universities will offer very good engineering programmes. Imperial will have more prestige I guess, but Bristol and Southampton will probably have more links to Engineering companies.