In total, I have 3 offers - Vlerick, Cass and HHL for a full-time MBA.

I need some help choosing between Cass and HHL as Vlerick being in Belgium won't be the best among these. I'm at the A1 level of German and by the time I start, I should be at A2 level.
I know for sure that by the time I'm done with the program, I would have achieved B2 level. So language is not the criteria as well as the UK work visa. I want to know the overall quality, reputation and post-MBA opportunities of these 2 schools. Please help!

B2 will limit you to back office roles. HHL and Cass are not very similar schools. Cass has better outcomes. Take a look at the post linked from my profile page on best MBAs for international students placement.

Hi Duncan, Thanks for your response.
I saw the post you mentioned but Cass is not mentioned there.
Would you say that Warwick is much better than Cass?

Warwick is generally better. In particular you will see it gets students into work much more quickly than Cass or HHL.

Okay. I need to respond to Cass within the next 3 days and I'm on the waitlist for Warwick and they have confirmed that won't be able to respond before the end of this month. Should I forgo Cass and wait for Warwick to respond? It is obviously highly risky. What would you suggest?

Btw, my fiance is working in London at BCG and I could work on her visa as a dependent post-MBA.

One option: Explain your situation to Warwick. Get them to promise that if you can't get off the waitlist you can join the London cohort of the DL MBA or EMBA. Then use the part time format to intensively job hunt as an experienced hire.

Safe route: go for Cass. You'll be fine.