I did this as my first ever race in 2014. I think that a TT set up is best as long as you are comfortable getting up the climb. The time savings after the climb would be considerable on a TT bike. I have a boardman air roadbike but I used it with the straight seat post and clip on bars and this worked well for me. There were a lot of TT bikes which went past me and a lot of disc wheels too.
Cheers Gareth. Think i'll stick with the TT bike then. That was my gut feeling, but you can never be sure. Thanks for taking the trouble to comment. Matt