Hi,

I am Brazilian and recently went to UK and the cheapest flight from SP to London is with TAP or IBERIA.

The flight stop at GUARULHOS (the international airport in São Paulo) and you can take a flight Fortaleza with GOL Airlines. Maybe you are supposed to change CONGONHAS (the national airport in São Paulo) but there are free bus transfer for passangers.

Also, check a travel package including hotel accomodation. In my case, it was cheaper to buy this package to London for 4 nights than pay only for the ticket.

Regards,