Thanks to everyone who has replied so far! I wasn't expecting so many fast replies!
With regards to the course itself, I am aware that the Cambridge course is more theoretical but I've spoken to a few "senior" engineers within the industry I hope to work in (Motorsport) and I was told they they're equally happy with graduates from both courses. I suppose that you mainly learn on the job so having a better understanding of engineering fundamentals just means that you'll have a steeper learning cure with the practical side of things.
Also, it's a good point that I would be given college accommodation at Cambridge and this makes living cheaper. However, I would receive a bursary from imperial and a larger student loan for living in London so the difference in how difficult it would be financially is negligible.
Personally, I feel that I would probably enjoy living in London for the social side of things more so than Cambridge, although this was one of my main reasons for starting the thread! I know both courses are very intense but I'm concerned that going to Cambridge would mean writing off any chances of a reasonable social life if I am to stand any realistic chance of getting a first or II.i...
At the end of the day, I want to study whichever course will benefit me best in the long term but I want to enjoy university and not spend every second of my time studying (obvious, I know...)
For anyone who has had to make a similar decision, how did it work out for you?