I've just had a look. Ultegra hydro groupset is 660 quid, 105 is about 200 less. I don't think it's worth getting all piece by piece unless you go for used. Wouldn't get used hydros
If you want it on the road ASAP I'd get the cheapest with the intention of replacing it soon. But if you have time build up funds a bit and you'll be much happier on good tyres and a pair of wheels that does the frame justice
I've just had a look. Ultegra hydro groupset is 660 quid, 105 is about 200 less. I don't think it's worth getting all piece by piece unless you go for used. Wouldn't get used hydros