Hey wahmed
Your question does have sense, but it's almost impossible to answer!
Depending on your budget, you could travel around from North to South, Italy is a really big country with lots and lots of wonderful places to see!
I'll try to give you a few tips, but of course, if others have anything better to add, i won't mind at all!
So, will you be travelling by plane or car? Either way, seeing how you're from the UK, Northern Italy is much closer and quicker to arrive to, as opposed to visiting the South. So, if you're on a budget or would like to save money on transport, I think 'landing' in the North is more convenient.
Here, I'd say focus on some of the most important or famous landmarks. For instance. you could travel around from Lake Como to Lake Garda, if you want, or you could travel around from The Adriatic Sea to the North-West part of the country. Basically, you could visit Venice, go along the East coast, visit Rimini since you'll be close by and in the summer it's definitely worth it! Lots of fun to have over there! And then you could travel around and 'end up' in Genoa (and surroundings).
Another option would be to visit central Italy, see Rome, see Florence and definitely see the islands!
Or, you know what's left? The South
I don't really know much about Southern Italy because I've never been, but in any case, whichever part or parts of Italy you choose to visit, make sure you do a quick search (on this very forum or on Google) to find out what landmarks are worth seeing (so you won't miss any!)