Broomie, you are entirely correct.....Mr Trigger, an F20 'box will NOT last long, as torque through it, NOT BHP will kill it before anything else.
The whole idea of the conversion (I assume) is to make a "slightly modified" car outside have the get up and go of a leopard on steroids inside, and therfore "fool" a few idiots in hot hatches that you are easy meat for a burn around the block?

May I (humbly) suggest as somebody who has a load of experience in putting big engines in little cars that you do the weight/bias/gearing calculations FIRST, and make sure your brakes and transmission exceed the potential performance by 30% minimum, because the potential momentum/weight/BHP figures (to be safe) have to be exceeded by the braking weight over trim balance point by 25%.
Advice if you need it, just PM me. Please ensure you also seam or stitch weld the major parts of the shell too, as the stresses you intend to inflict on the shell exceed the manufacturers build construction parameters by a lot. The Corsa was never designed to accept any more than 160 BHP, and the "chassis" welding and design was not welded or strengthened sufficently to accept the added weight and torque you intend to fit.
Not telling you how to suck eggs at all, just gently advising.
Mike