I have a hole about 2" diameter in the neerside inner wing. Is it an MOT failure? the inner wings are available from Paddocks, shown as require modification? What modification is required and has anyone fitted them? How easy is it and how long would it take?

Depends if its within 30cm of a body mount, if not then it wont fail.

For a hole of that size, I wouldn't replace the whole inner wing, any competent welder (me!!!) would be able to repair it.