Well, Southampton is a fairly different prospect to living in London, as it's a much smaller city. That said it's not overly far on the train so visiting London on the weekends is certainly possible if you find there's not enough in Southampton to do!
Southampton's chemical engineering course is new and hasn't had a graduating cohort yet so harder to tell exactly how it's turning out. That said it's based on a collaboration between the chemistry and engineering departments there, both of which are very strong. So that may be encouraging! There is also a nearby chemical plant where you might be able to get some local internship/work experience opportunities (the Fawley Refinery)?