Vitus Zenium Carbon Frame Bike with Tiagra Groupset £869.98 delivered @ Chain Reaction Cycles

I am not sure if most people really need 105, or would be able to notice the difference between today's Tiagra and 105.

I have cut and pasted the summary section of the roadcc review of the R4700 groupset.

Conclusion:
Is Tiagra worth the money?Tiagra is a really impressive groupset. To get this level of performance, finish and attention to detail on such an affordable groupset is hugely impressive.

It's both better looking and better performing than the previous Tiagra, and in the changes that Shimano has made, the gap to the more expensive 105 has been significantly narrowed. The most notable improvement is the updated shifter bodies, which function very similarly to the more expensive groupsets, with the same shifter body shape. And the new chainset is a much better-looking bit of kit too. It doesn't look cheap, it looks expensive. That's good.

If I was buying a bike with the new Tiagra groupset, such as the Raleigh Criterium Sport, I would be very happy indeed. It does everything you want from a mid-level road bike with only a few very minor quibbles. The biggest decision to make when buying a bike at this price is whether you're really fussed about having the 11-speed of Shimano's more expensive 105, and will come down to your budget.

How about if you're building your own bike? At retail prices, the difference of around £100 between Tiagra and 105 might make it worth saving up a little longer, if only for the better brakes, small weight gains and the upgrade to 11-speed, which better future-proofs your bike against any purchases down the road.

If you're buying a new road bike with the latest Tiagra, there's no doubt about it, you're getting a better bike for your money.

Verdict
Improved ergonomics, appearance and functionality make this a big step forward for Tiagra (edited)

Best guess would be medium, but check for sizing on the web page. They often give sizing based on height and inside leg measuresment. If between two sizes and can't get to a shop to try one that I would always go to the smaller size, easier to make a smaller bike "longer/taller" by adjusting / changing parts, rather than trying to make a large bike shorter/lower.

Also note thay one brands medium or 54cm may not be the same in another brand. Generally mediums will fit people up to 5ft 9in (i.e. me), often I am pushing towards a large but prefer a smaller bike.

100%

Do you have a daily quota of comments about disc brakes? It's getting old now.