Ok, then you have unbalanced H&C supplies. One high pressure, one low pressure.
You'll need a mixer that should be described as "suitable for low pressure systems".
With older taps, this was not a problem, because the "tails" that connect the tap to the supplies were 15mm.
Modern taps often have braided flexible tails of a very small bore.
This often causes the cold to overpower the hot, making it a little more difficult to mix the water properly.
Taps suitable for low pressure are essential, but the restricted tails will always unbalance things. It'll work, but I just wanted to point it out to you.
Have a look through this lot to give you an idea. The descriptions will tell you if they're suitable or not.
https://www.screwfix.com/c/bathrooms-kitchens/kitchen-mixer-taps/cat4650002?colour=chrome
You say you have been unhappy with the current one. Maybe that one is not compatible with low pressure.
Do mention the tails to your plumber. He should certainly be able to advise you.