HEC vs LBS vs LSE

I actually think HEC = LSE in London in terms of reputation alone. They're all top tier in Europe and will give you access to interviews in most banks.

Personally would go for HEC. A couple of points to have in mind:

• HEC is MUCH MORE networking oriented and HEC alumni will heavily favour HEC candidates (heard of HEC students receiving the case studies in advance of the interviews..). They also bring you to London at the offices of top banks and PE funds to network on site. The same cannot be said for LSE - tons of them in London, so the brand is well known, but the alumni support is minimal. +1 for HEC
• If you're gonna work in London, you may want to have an international experience before starting your career. +1 for HEC
• Visa will be easier coming from LSE. That being said, most large banks sponsor now. Neutral.
• HEC will be a lot more fun than LSE. Generally, London is not as fun as a student as when you’re working, because it’s so big and expensive. HEC offers a campus experience outside of Paris, active student societies and open bar parties. +1 for HEC
• If you have any hopes of working abroad (US / Asia), LSE has global fame there while HEC does not. +1 for LSE
• In terms of the course itself, it shouldn't be your main concern but LSE will be quite theoretical while HEC will be quite practical (it's a business school). Neutral
• One argument that LSE has going for them is the historical perspective. Many Nobel prizes and presidents graduated from LSE which is arguably one of the best universities historically after Oxbridge and Harvard Princeton Yale. Top tier in economics and politics. Consequently it has a bit of a cache is is very well placed in global rankings, consistently top 5-10 worldwide in its subjects. HEC/LBS in contrast are more niche to the business crowd.  +1 LSE

I don't know as much about LBS, more networking oriented than LSE, but perhaps slightly less prestigious (I feel the brand name is a bit diluted by the quality of candidates in their MBA programme). They place well though, and the alumni network is very active. Perhaps on par or slightly above LSE in London (due to the career center). Placement outside of the UK will be the main negative here as I imagine it's not as well known as HEC in Europe or LSE in the US/Asia. 

In terms of networking, agree it won't help that much in London (although definitely can't hurt and a friend of mines got his offers through networking) unless at structured events like with HEC.

Source: I went to the LSE and to another French business school.