The eBay bike looks ok and good value at present with the Ultegra kit. But it doesn't really stir the blood, therefore will it inspire you to ride?
Road bike fitting is pretty straightforward really - if it looks right then it probably is and then just a few tweaks to get it just so for you.
There are loads of ways to calculate the 'perfect' road bike fit and the following include online calculators - depends on how detailed you want to be in making measurements reallyhttp://www.competitivecyclist.com/za/CC ... ATOR_INTROhttps://www.wrenchscience.com/Login.asp ... tylecode=Rhttp://www.bikeradar.com/mtb/fitness/ar ... 4608?img=2
(MTB saddle height but works as a rule of thumb for road bikes)http://www.corktri.com/documents/FVBSC_FitArticle.pdf
Worth stressing though is yo go with what works for you - as an example, compared to many measurements I ride with my saddle too high but it works fine for me. As a contrast I'd contend that many people ride with a saddle slightly too low (although this may just be my way of convincing myself that I am right).
Have done my measurements with the following results
The Competitive Fit The Eddy Fit The French Fit
Seat tube range c-c 51.0 - 51.5 52.2 - 52.7 53.9 - 54.4
Seat tube range c-t 52.6 - 53.1 53.8 - 54.3 55.5 - 56.0
Top tube length 59.5 - 59.9 59.5 - 59.9 60.7 - 61.1
Stem Length 11.9 - 12.5 10.8 - 11.4 11.0 - 11.6
BB-Saddle Position 77.0 - 79.0 76.2 - 78.2 74.5 - 76.5
Saddle-Handlebar 56.6 - 57.2 57.4 - 58.0 59.1 - 59.7
Saddle Setback 1.5 - 1.9 2.7 - 3.1 2.2 - 2.6