Which Groupset?

The initial price difference of tiagra and 105 is very tight, IMHO unless the wheels can't handle 11 speed don't see why would choose tiagra.

Nah you were right - price difference between Tiagra 4700 and 105 5800 was under five quid.

Quite a few of the 105 parts were cheaper than Tiagra, including the brifters by £22. I think only the chainset, cassette and rear mech were more expensive.