The radiator is a double panel with fins on both panels, commonly referred to as a K2 radiator. This is what the radiator schedule says you have.
That is suitable for a heat pump and from everything you have said the radiator you have should be more than adequate.
Thanks also for the information about your kitchen. The good news is that the heat loss sounds as if it has been done correctly and your radiator should be more than adequate. So the good news is that there are no fundamental errors in the design and you have a setup that should be capable of easily heating your kitchen.
The bad news of course is that it isn’t.
Radiator balancing - this could be where your problem is. Radiator balancing has nothing to do with where the tank or heat pump is located. Its all to do with how much water is allowed to flow through each radiator compared to the others. If we go back to your original radiator schedule to the Coverage column. This shows that some radiators (like the bedrooms) are around 100% coverage, i.e. they will put out just about the right amount of heat to match the heat loss of the room at design conditions. Other ones (like the kitchen and the hall) show about 190% coverage, i.e. they put out nearly double the required heat than is being lost. All things being equal the hall, kitchen, WC and to some extent Living Room should heat up more than the bedrooms.
What I wonder is whether the installers attempted to balance the kitchen radiator to reduce the heat, and have overdone it (to be fair its not a straightforward task to get right at first attempt). What this means is they will have restricted the amount of water that can flow through the kitchen radiator. If you look at the radiator there should be a valve either side of the radiator, between the pipe that comes up from the floor and the radiator itself. These should have some form of adjustment, it might be a knob or you might remove a cap or something and then turn it will an allen key.
See whether you can increase the flow by adjusting these (anti-clockwise rotation). You’ll then need to leave the heating running for a few hours and see if things have improved. I’d reduce the flow temperature (using the heating curve) back to what it was before doing this.
If its not clear what I mean, can you take a photo of the connection between the radiator and pipe on both sides.