London vs Zurich vs Frankfurt

Apply everywhere, get an offer from one or some of these schools first then come back

London via LSE/Oxbridge is your best bet. Bocconi/UCL/Impeial  and HEC Paris (this one I think is only Master's though but not certain) are solid also and could work out well for London. 

Switzerland is amazing imo in terms of quality of life but if you are non Swiss I think it will be very tough to land a good offer there. 

Frankfurt isn't as fun as London but it's like 2.5 times cheaper (especially when you get older and get kids) which can help you build wealth quicker under less financial risks/fixed costs compared to London IBD. There are very few meaningful PE exits in Germany though. HSG and WHU would be targets, LMU and Mannheim while good universities aren't targets. Without B2 German you would have an uphill battle. Biggest downside is that many internships are often off cycle and are not structured to give you a full time role if you did OK as it's the case in London SA program I believe, at least this was the case in the past. The job market here is surprisingly not too bad for IBD if you look at a ratio of number of entry level roles to number of qualified applicants. 

As someone who grew up in the UK, did bachelor there and is now doing a masters at one of the German schools you mention I’m going to disagree with everyone else and say that if you want thread into IB you’ll have the highest chances here in Frankfurt - but with a big caveat - you almost have to speak German. 

If you do, the amount of internships you can do and ppl do here is crazy, and recruitment in Germany is a lot easier than  in the UK. The UK has moved away from networking and also I believe targets are becoming less and less important as they move towards almost entirely blind recruiting, whilst in Germany it’s common to only have 2 interviews, entirely technical with very few behavioural and motivational. That being said, the Germans are extremely snobby. Not so much as to what school you want to (even though it helps)  but your CV won’t make it past the first stage unless you already have relevent exp. At similar calibre firms. Hence why you need to build up your experiences, whilst in London in theory you could walk straight into an M&A summer at JPM with no prior exp, and here that would never happen. German bankers here also don’t value UK internships in the same way because of this.

It’s also important to know that Frankfurt is a lot cheaper, and intern pay is a lot lot lower, like almost minimum wage or just above. Not like in London where it’s pro rata analyst pay. 

IB as you know it won't exist by the time you graduate broski

The recruiting pipeline is obviously much bigger in London, but that doesn't mean recruitment is easier. Just means you in theory have more chances to land something. I would study something prestigious but local within DACH region, do the typical German multi-internships, and you should be in a strong place to go into IB. Apply to all of these markets, the most important thing is to get your foot in the door with a full time analyst offer. Once you've done it for a couple of years then you can lateral to where you actually want to be longer term.

I would not blinker yourself to a region for recruiting purposes, but I do think the internship structure is better in DACH and it's more typical to get multiple competitive internships under your belt and finance societies and Unis are geared around that.