British Airways fly to Pisa and Genoa from London Gatwick daily and flights from Manchester during the summer schedule.
Often during the summer months charter airlines offer flight only deals from regional airports, and can sometimes get a good deal last minute, contact your travel agent or flight centre. They can arrange travel insurance as well. With regard to travel insurance ask about a years policy as normally it is more economical should you travel a few times a year.

(always check terms and conditions on your airline bookings, normally the cheaper the fare, less flexible the ticket)