When it comes to social life, small is beautiful. There are only around 4000 people on campus at any one time, but chances are you will know most of them by the end of your first year. Aston is an exceedingly social place mainly because so many people live and study on the same tiny campus. You can't help but bump into people left right and centre and of course you are right in the heart of Birmingham so it isn't as if you are short of somewhere to go.
The only downside to Aston is if you want to continue hobbies and passions. There are a great many clubs and societies but due to the small intake, the standards tend to be a bit lower. As a result, I continued my music at Warwick University. That said, where clubs fall down on ability, they more than make up for it in friendliness and I found my now long lived passion for climbing and mountaineering at Aston.
Compared to the vastness of campuses like Manchester and Liverpool (places I am now very familiar), give me the friendly close nit community of Aston any day.
Oh - and you are right - the courses are highly regarded at Aston and the ease of having a sandwich year (whether you applied for it or not) in your degree is a must for any ambitious person.
Good luck!