I don't recall anyone promising tax cuts during the last UK general election
Yes, the Tories won despite promising more austerity and that's the big difference between the UK and Greece. Regardless, if they thought it was affordable they would definitely not hesitate to use windfalls from taxing foreigners to buy off pensioner votes, for example. That's a very clear pattern in how governments do things.
And we spend 8% of government spending on interest not 25%.
You're right. I looked it up and it's 8%. I'm not sure why I thought it was 25%, perhaps I'm getting confused with some other country.
But the main point is, if a company wants to do business in the UK it should pay UK taxes on it's profits.
We're talking about a company that delivers things through the mail, here. What does "doing business in the UK" even mean? If Amazon were to have no offices or presence in the UK at all and just deliver everything via third party companies, would they be "doing business" there or not?
The problem with this sort of thinking is it ignores the consequences. Imagine a small company in the USA gets an order for its new widget from the UK. The company wants to sell, but ...... wait! The UK has screwed up laws. A single sale to a British person means the UK Gov will classify the company as "doing business" in the UK and suddenly all the companies profits are taxed twice. No can do, therefore, no sale.
So in practice that's not how the system works.
What about first employee in the country? Well, same problem. Google looks at the UK and says, hey, we'd like to hire people in Britain to do engineering and sales. But ..... it makes no sense, because hiring the receptionist for the new office will cost us a billion dollars in new tax, as suddenly our profits all get taxed twice.
So the scheme you outlined is not workable. It'd just mean nobody does business with the UK.
The usual variant people demand is "tax only the profits made in the UK" but this is also so vague and poorly thought out as to be unworkable. Where are profits made, exactly? This is easier to see with a company like Google or Facebook. The physical location where profits are made is unknowable because many countries contribute to the whole. For Amazon people tend to say, it's the sales to people in the UK, but then you're asking for a sales tax not a profits tax, and the EU VAT changes have now put this in place (at massive bureaucratic cost).