I can't speak for Italy, but the general strategy is frowned upon by immigration officials. Assuming OP is US citizen, and wanted to go to UK for 5 months, going for 89 days, then a month in Europe and then back for another 60 days would raise a lot of red flags. Maybe they would get away with it, but maybe not.

One way to perhaps 'finesse' it, if funds available, is to book a flexible (fully refundable) ticket, perhaps a week after the second entry to Italy. Use that for evidence that this is a short trip (if asked), once in the country, cancel it, and stick to original itinerary.

tb