Any recommendations for a cheap aero bike? €1k to €1500ish. Would like Shimano 105 or similar. Or alternatively a good all round race bike for the same price. Thanks
Road, TT, or triathlon? Recreational use or mixed in with race use? Road or criterium? These will help people point you the right way. People buy race bikes for varied reasons, so know use helps. Recreational use, sure, keep with the 105. If actually racing, I'd say make the move to Ultegra.
The used and new bike markets are still tight. But that's the way I'd go. In that price range you're looking at pretty much only lower grade "open mold" framesets and a used group set to put something together in that price point.
If I had those euros, I'd probably try to find a used alloy Allez or something with 11spd Ultegra on it then spend the rest on a power meter if it doesn't come with one.
A good (not cheap quality) open mold carbon aero frame for road or TT these days is still almost be $1000. A full used group set in just 105 will set you back the ret of what you're budgeted. This is why I'm steering you used on that budget.
Not to mention some modern width wheels with GP5000's and latex tubes will cost you a little jingle and make a difference if you don't already own some.
For road race bikes my priorities on speed for things you actually buy has personally been:
-aero road helmet
-"onesie" style suit like a Castelli San Remo
-GP5000 or similar and latex tubes
-aero handlebars
-aero wheels
-lastly........aero frameset