Convert Existing Site in Responsive Design

We are interested in converting our existing website mobile Friendly. Therefore we need the site to be redesigned using Responsive Design so that it works in All devices. The site is created in PHP, MYSQL. Your suggestion is most welcome if we should do it in PHP MYSQL or Use Code Igniter. I am not familiar with other Frameworks and will not be Interested. There are About 20 Unique Pages to be created. Once the First Page is completed, The Header , Left , Right and Footer will be Ready and Will be used in Other Pages with little modifications. The Design Must be very Good. We would need to see your Past works on this. There are Two Websites to be Redesign which is created from Same Codebase. Performance of new Site has to be very good and should be < 2 - 3 Sec. We will use website performance tool to see the performance before accepting the work. We would like the Page loading for each page should be less that 3 sec. Please provide example of your past projects, similar is better. Our site is not too big which I can take you once the bid is placed. We will use Twitter Bootstarp with PHP , AJAX , MYSQL Another important thing is the Migration should not change the Link Structure of the Site. To ensure this we will test the links through a crawler if possible. I AM BASED IN UK, IT WILL REQUIRE DAILY CATCHUP IN THE EVENING ( IST 11:30 + ) SAY FOR 30 MINS. IN CASE IF YOU ARE NOT AVAILABLE DURING THIS TIME PLEASE DO NOT PLACE BID AS THERE WILL BE COMMUNICATION ISSUE