I need a professional App Developer with lots of experience.

General information for the business: Chat App similiar to Whatsapp but with a timeline.
Kind of development: Customization of existing program
Description of requirements/functionality: Opening of random group chats required as clicking on selected groups.
Extra notes: I am developing an Social Network for Iphone that will use mainly XMPP technology, where users will be able to send contacts, photos, locations and videos. Very similar to Whatsapp but intended for groups instead, there will be a tab for individual chats and another one for groups (similar to a forum). The data will be stored both on the user phone(private conversations) and on the cloud (groups). The registration will be made by phone number and the users will also have a short profile with name and picture. This same App will have more features on the future, so the code must be left open for our team. The code will also have a space on the bottom for the ads. Our target audience is worldwide, so the code needs to be easily to understand to update to any other language. Our aim is to reach 250,000 users in 6 months.
The content, graphics, design and UI design will be provided and the platform is for IPhone initially, but it will be done in future for Android users. So, the code will be possible to convert to another platform with minor changes.
We are only interested in UK based developers, and this developers must be able to travel to London for the interview. Previous experience required. More info will be provided after the NDA is signed, but you will be programming and handling a blank layout that will be re-skinned from another person. Please, get in touch through people per hour ONLY. Thanks