OP you will have a great time here. In zurich there is always a party happening, plenty of night life. If you are into the outdoors it's now summer so there is loads of stuff to do, biking, climbing, hiking, sailing, water rafting etc etc... If you do move into that WG it will be a good way for you to meet new people and is probably a good idea for a young person to do that first.

What are your interests? you said in a previous thread that you've had a very busy 4 years in London, I bet when you settle in here especially if you decide Zurich then you can equally have a pretty busy life here. Switzerland is though a more relaxing place than the UK so it will be a lot different to living in London.