Update.
After going through 2 bonnet catches to try and get the new bonnet to actually lock properly I (well my dad) discovered what the problem was. The new bonnet just wasn't coming down far enough no matter how much we adjusted stuff so out of curiosity my dad straightened out the old bonnet and put that back on. Bang, shuts and locks 1st time. Opened it, closed it, locked again. So now I'm back to my old bonnet with the massive dents etc but at least it shuts.
The thing is I always thought all cinquecento bonnets were the same? The new bonnet I got from a scrap yard from a cinq S, but it won't shut on my sporting. Sporting bonnet, shuts first time. Work that one out lol.
Red Cinq Sporting Abarth 1242