It isn't that simple. There isn't a linear relationship between the tax % and the revenue to the treasury. Lower taxes encourage more companies to set up in the UK.
We saw this recently in the UK when the top rate of income tax was raised to 50% and the income to the treasury actually fell.
As I wrote, the tax cuts are being proposed to compensate for lower investment due to brexit, and it is unclear whether they will be able to compensate fully.
Ok but the numbers you quoted assumed a linear relationship.
In no way is it "almost certain" that investment in the UK will decrease. The evidence currently suggests the complete opposite. Look at the performance of the FTSE100 since the referendum to see the flood of foreign investment coming into the UK listed companies thanks to the weaker currency.
I'd also point out that decreasing tax rates is the exact opposite of what the chancellor said he would do before the referendum.
We saw this recently in the UK when the top rate of income tax was raised to 50% and the income to the treasury actually fell.
https://en.wikipedia.org/wiki/Laffer_curve