[m_t]

Probably because one of the reason people from the EU came to London and, in general, the UK, was because you didn't need a visa.

Remove that possibility, then people will consider other places as well.

[forgingahead]

I highly doubt people keen on going to London would consider Brussels or Frankfurt an acceptable substitute.

[gpvos]

Depends on where the jobs move to.

[raverbashing]

The ones that won't bother to learn a different language certainly won't

[royka118]

sure but the types of jobs on offer in London may not be on offer elsewhere.