Leaving the issue of legal/illegal immigration aside, do you think diversity is good or bad for your country?

I think it's very good. In UAE diversity pretty much forced people to act civilized so they brought up healthier and better thinking generations. In my country the cities that got diversity are way more civilized than the cities that don't.
The more diversity you find the more acceptance you see because it teaches people to embrace their differences.

its very good, it can open peoples eyes to whole new cultures and has improved the UK lifestyles and food 100%

Diversity is great if there is something holding it all together.

Good. But it can be taken too far.