By chance, did you remember to share the parameters to your project as well?

i thought I did but perhaps I didnt do it properly, refresh my memory?

I don't believe it's possible to assign a shared parameter to a dimension inside the titleblock family, the option to do so is greyed out when I look.

The shared parameter you are using then to create a text label is not the same parameter as what is reporting the height of your titleblock. Unfortunately i'm not sure if there is way to do this without being able to access shared parameters for your dimensions. How often does your titleblock change in size? why not just make a text label that is by type parameter and control the "height" text by family type.

The region where I currently work uses irregular paper formats.
Actually I find it absolutely stupid, but thats how it is.

For example instead of just using A1 or A0 (or other ISO standard formats)
They use a factor of A4. So this could be 3H x 12L of an A4.
So 3 times the height, 12 times the length of an A4. You end up with a plan that is inherently difficult to manage on site, and also there is tons of waste from your plotter. However, this is how they do it.
It can be one of 36 different formats. Yes I can just have it report a text value and assign a different text value based on some "standard" factors (ie 1H to 12 L of an A4, 2H to 12L of an A4 or 3H to 12L of an A4) But as I said this is about 36 different values to type oh and did I mention in addition sometimes the use 2.5H instead of 2. So there are also all the half formats to add in for 1.5 and 2.5 so thats another 24 possible formats.
In total 50 formats to add.
Its much easier to make the length and height modifiable and simply read the values in mm from the parameter - except bloody revit wont let me report these values. I have no idea why. It simply does not work.

well that is a pain...

It may be worth looking into Dynamo to get those Height and Width parameters and push them through to an available field of your label text. I'm not 100% sure what the nodes would be but something similar to this.

https://www.youtube.com/watch?v=-Qx_LT2Wsvs