My Question: Can anyone tell me a way I can express the single ring being
overloaded referencing the IEE regulations?

The ring should be capable of supporting the expected loads as well as the
100m3 restriction. I can't see how this could be said to be the case.
However, rather than an upstairs/downstairs split, it is most important that
the kitchen has its own. The loads in the rest of the house without electric
heating are likely to be tiny.

Sounds like they've blown the 100m3 anyway.

When partially rewiring my house, I've put several circuits just for the
kitchen. One 32A MCB radial powers only the dishwasher, washing machine and
tumble dryer. A 16A MCB radial does the fridge/freezer. A 32A RCBO ring
powers everything else (except lighting).

Christian.