My overall university experience was okay. Not good and not bad.
Teaching quality gets progressively better from first year to second year to third year, at least for the modules I have taken in second and third year. If you are used to rote memorisation through your high school studies, you might need a while to adapt to the teaching style as they throw you straight into the ‘look up answer for yourself before asking questioons’ route (not to say you cannot ask questions during the lectures or if you need clarification, but lecturers generally don’t appreciate it if the answer you’re looking for is written very clearly in the textbook). Some people adapted to it quite fast (in ~1/2 months) whereas for some people it can take longer (I took about 6/7 months myself), so don’t panic if you find yourself unable to catch up in the first few months.
Workload is fair for first year, drastically increases during autumn term in second year and final year is just crazy. Not to say you wouldn’t be able to cope, but just bear in mind that it is best not to do work last minute from second year onwards.
On the social aspect, I would say to just go out there and meet people! Don’t just mingle with people from your course, mingle with people outside your course as well. There are many brilliant ane nice people in Imperial. There are also 300 clubs and societies in Imperial and you would definitely be able to find one which you are interested in! If you have something you’re interested in but have no experience of, do not be afraid because the clubs and societies cater for complete beginners as well. I personally do not party a lot and can’t make much comments on it but as you are in London, expect everything to be expensive.