While I do not doubt that the carbs were made... a Hillman Imp GT is just as rare here in the U.S. as the 1.25 carbs.  Of course... the Jon (the OP) does have a signature that implies he is in Norway.  Imps were probably more common there.

Since the carbs probably are in Norway, Joe Curto may not be the best choice.  Burlen in the U.K. who supplies SU parts also supplies parts for Strombergs and Amal carbs.  Google for Burlen and visit their web site to see what they can offer.

If you test the carb floats and find that they are "sinkers" instead of floating (and both pontoons have to float), email me.  I have recently modified a late model CD2 float to fit an early CD carb.  If necessary I can explain what I did. 

EDIT:  I did a quick search and found a few links that may be helpful.  
First, Burlen:  //zenithcarb.co.uk/carburettor-kits/cd-stromberg-service-kits.html
Second a Blog on Marine Strombergs:  //ckdboats.blogspot.com/2012/05/how-to-service-zenith-stromberg-cd125.html
(Note there is a link at the bottom of the page above for what appears to be the author's Stromberg parts source)
Third, Gower & Lee in the U.K.:  //www.gowerlee.dircon.co.uk/spares.html#Stromberg
(It looks like you would need to contact them to see what they can offer.  Their web site doesn't show a lot).

Twin CD125s are not that rare, they were used on the Hillman Imp GT. My brother has a couple of sets (we are currently rebuilding a motor to use a pair).

If the carbs are overflowing just make sure that the vent for the float bowl isn't blocked or plugged.
I have seen this happen on both CD's and SU's. 

I like CD's they are a very neat carb. I used to run them on race cars years ago. 

For a unique size Stromberg like you mentioned I would make Joe Curto my first call.  Good luck with the process.

Great, thanks! my main problem has been to find replacement parts, so I appreciate Your answers a lot 

I didn't know that Minis ever had Strombergs even from special tuners.  It's a curious choice.

Are these CDs or CD2s?  The original CD carbs will have a jet that you adjust from below like an HS series SU.  The CD2 carbs came later and have a fixed jet and you adjust the carb needle from above instead.  

You may simply have float valve issues as Cup Cake said.  The float valves should be availalbe from many of the suppliers for Triumph cars although, most Triumphs use the 150 CD or larger.  If you give Joe Curto a call in NY (Google him) he is likely to have the float valve you need.  Buy some float bowl gaskets at the same time.

To adjust the floats on a Strombergs the carb needs to be off the car.  With the float bowl removed you invert the carb body and you have to bend a little tab on the float arm to get the "highest" spot on the float adjusted to the "correct" value.  I believe that the float height figure is 17mm but that number is for the 150 and 175 CD sizes.  You'll need to Google for confirmation that is correct for your 125.

While you have the carb off to replace the valve and set the float height, remove the float and place it in a cup of gasoline.  Both pontoons of the float should be "up".  If either sinks in the cup of gas then the float has a pin hole leak.  If either pontoon sinks, the float will ride "low" in use and you will have flooding and driveability issues.  Floats for the original CD series are NLA.  Floats for the CD2 carbs are available for the 150 and 175.  Hopefully they are also for the 125.  This is another thing to ask Joe Curto about when you get him on the phone.

You're close ... the word is floats. It sounds to me the float bowls are over flowing. This usually indicates the needle valves that control the fuel flow need to be replaced.

Anyone got any experience with the stromberg cd125 carburetors on the mini 1275? I got a pair on my mini, and they tend to overflow with gas, sending the excess gas into the airfilter. I have tried to adjust the floaters (is that the correct english word?), but without luck. I do not know what the factorysetting for the floaters on these carburetors are. I have done some research online, and found that the stromberg cd125, was delievered by a company called alexander tuning, or alexpress. If anyone has any information, i would much appreciate that.  

Jon

Norway