This obviously means you should be going for 105 Di2. You know it makes sense.
Just a
leetle bit more money and you could have it
That said, I just put "Tiagra Hydraulic shifters" into Google and they seem to be £150-250 per
pair. Now maybe Google's showing me the wrong stuff, and I know that doesn't include the brake calipers (or whatever they're called) and hoses and gubbins, but the brifters will be the most expensive part. Are you
sure you can't do it for less?
Merlin have this for £300. Is this all you need or do you need other bits too ?
Shimano Tiagra ST-4720 Hydraulic Disc STI Levers & R4770 Flat Mount Disc Brake Set - 10 Speed
https://www.merlincycles.com/shiman...lat-mount-disc-brake-set-10-speed-247267.html
(I know nothing about disc brakes, hydro or otherwise)