@d3vy - nope I'm not suggesting you put income tax up just stop some of the "creative" ways big companies and governments for that matter get around "paying" their top direct and indirect staff so that their income tax bill is drastically reduced.
There are lots of reasons for basing your company on the UK instead of East Elbonia, not least of which it's hard to get your top talent to relocate to a mud hole. A higher wage bill can be money well spent. Also if UK companies paid no company tax it would remain an very attractive place to head up your business even if the employees couldn't avoid tax on their pay and shares.
As for the numbered questions:
1 Freed from the burden of company tax small companies should do well. The tax is just shifted to the dividend paid to the shareholder.
2 Freed of their tax burden the companies will make more profit that goes back to the shareholders as a bigger dividend.
3 Fine if they are living in the Caymen islands, they can have their bank accounts there and pay tax there but if they are tax resident in the UK they will be taxed on their foreign earnings.
The moderately well of people don't bother with off shore accounts. They are too busy getting on with life to ever get around to minimizing their tax bill.