Transit Without Visa Question TWOV

[smp10484]

Hi, my fiance is a Peruvian with a US Greencard. We are honeymooning in Europe and our flight is to Dublin via London. She has receieved a Schengen visa and Multiple Entry Irish visa already. We have a 12 hour layover in London.

My first question is will she be able to leave the airport with a TWOV? I have been to London many times and would love to show her the sights for a few hours before returning to the airport.

Secondly, we are making our travel arrangements and have noticed it would be cheaper to fly to London or Edinburgh from Dublin then onto our final destinations in Europe than fly directly from Dublin. Would this be an issue if we were using low cost airlines without a though intinerary. IE Dublin to London on RyanAir then London to Greece to EasyJet.

Any help with these questions would be greatly appreciated!