Structural engineer error

Good evening everybody,

I wanted to ask the consensus on here.

So I have begun my self build with a raft foundation being cast. This has cost a considerable amount being a large detached plot.

When the setting out engineer came to pin the corners on the raft for the brick layers he noticed a discrepancy in the structural engineer plans who designed the raft and the architect plans.

In essence the raft is 240mm too long and too wide.

Looking back on the plans, the earlier raft design fit perfect with the architect’s drawings however as new drafts have been made it appears some of the dimensions have become bigger.

This hasn’t been picked up by anybody but there was no reason for it to grow in size.

I am now in a position where my development is 24cm larger than it should be on planning through no fault of my own.

I have approached the company director for the structural engineer who accepts that the dimensions have become slightly larger but cannot tell me why. Further more the actual structural engineer has left the company.

The issues I have now is because this is being built on raft I don’t have any wriggle room to move the external walls, unlike a traditional strip footing.

So my question is, anybody ever experienced this?

And

Would you think a section 73 material amendment submission (not 73A) would be sufficient and what are the consensus on this being granted?

I am not in a conservation area nor am I encroaching on neighbours land.

I’m really frustrated as this is now causing delays and further expense through no fault of my own.