You can't get a tip unless they make one that has like a u-bend in it. Never seen it though. I had the same problem with first Fiesta (57 plate) I had to go and get a back box professionally fitted. It cost £130 so it's more than what a tip would cost but well worth it as you get the sporty noise to go with looks. Depending on the style you get it can also come under Neath the bumper (I didn't want to cut through the bumper, when I sold the car I removed the backbox and put the standard one back in).
Hope this helps
Believe this was you? Is this not an option then? Sounds perfect for my situation if true?