try bike exchange, worked for me when I was over there (I'm 172cm so not tall either). For sizing, top tube length is the first place to start. Most modern stuff comes with a height recommendation which is normally enough to start with, then do the rest with seatpost/stem changes (unless unusual body shape). Over there I picked up a small tcr advanced, whacked a decent stem on it and have been riding it since (now in NL).
As for the route, its hilly but on par with the weir. You can come up red hill on the way out if it isn't enough, and then loop back to Chidlow and John Forest. the small parts of toodyay used to connect up aren't too bad for a highway, wide enough for the road trains to not be too much an issue.