I'm a structural engineer, can I do my own calcs for my extension?

If you do need to submit a planning application, you will have to create drawings in a standard architectural format for inspection by anyone who may potentially be affected by the work - e.g. the owners of neighbouring properties. The planning department will notify them of the application to give them opportunity to comment on it before it is approved. These drawings don't specify the technical details of the construction, but show the changes to the appearance of the existing buildings. Whether you need planning permission or not, the work needs to comply with the UK building regulations. In general, as long it meets the required standards. AFAIK there is no legal necessity for any form of insurance qualifications either on the work itself or the finished building - though it would be foolish not to have insurance against third party claims if there is any risk of a disaster damaging other people's property, but it’s your home you’re the owner will take full responsibility, that why building company have full Public liability insurance Hope this helps

As listed g as the calcs check Out I can’t see why not building control will need to see prior to installation of so called beans.

YES YOU CAN.

Building control check your calculations so no problem

The BC will have no problem accepting your calculations. You on the other hand have no PI insurance and therefore the onus will be upon you to ensure your calculations are correct. The issue here is not BC but your home insurances