I currently have a valid UK and US Business visit Visa (Both are multiple entry visa's). I will be travelling to Portugal next month and my flights are from Mumbai through London to finally Porto. My travel agent was booking a ticket for a flight which will be landing in London heathrow airport and then get on another plane from Gatwick airport (with 5 hrs transit to get to gatwick)... my question is ...do I need get a transit visa or can I manage with the UK business visa which I already have and have been granted a business visit visa to enter UK.... It would be few hours in London just to get to another airport within London. I will be getting a Schengen visa to enter Portugal. .