If the new carb is UK spec it will be right for your car if its a standard engine. If its had any cam, head or piston work then you will need to factor that in.
Check that the accelerator cable is fully returning so the idle fueling is right hence initial mixture can be set.
It's worth taking the air filter off and looking down the barrels at idle to see that there is no overfueling occurring or dripping into the second choke caused by it not shutting off at idle. This can cause a problem with set up.
@Dave Knight car has a strange adapted bracket for the accelerator cable which means the link rod is not straight. I plan to remove and reset to get things back to stock.
It takes a bit of playing to get the right mix and timing to suit the individual car. Thankfully webers only have 2 screws and the dizzy is on the same side too.
The other thing to check is that you don't have a vacuum leak on the base gasket. One of the mounting studs is awkward to access and can prevent even tightening.
I've needed 6ft arms in the past.🤣