Get a large frame, Its more suited to your height. If you want to buy new you can always go for a Triban 520
Secondhand wise, Triban 3 is a good buy providing the frame is in good condition. you can pick them up fairly cheaply on
ebay then chop and change whatever you want on them as you desire. Definitely change the wheels though. you might want something a bit lighter then what the original T3's came with. secondhand 105 or Tiagra groupsets shouldnt cost that much and that will help keep the costs down.