I am not the best person to ask. My travel is almost all business while I am there. So I am just at our offices or at the hotel when I am using the internet.
From what I know, Paris is pretty good for wifi and London is not as good as Paris. Again, that is based on limited personal experience. Maybe someone else has taken some holidays to EU and can answer that question far better than me.
Sorry I can't be of more help. You know nothing would please me more than to be able to offer elite advice with regards to EU travel.