With today's announcements of Elbow and Public Service Broadcasting, I was tempted to book Latitude, which I really liked during my one visit in 2017. But ultimately it was just too expensive, especially since I'm coming from abroad and would need to book one of those Pink Moon pre-erected tents. Ultimately it would end up being over £600 for the festival and tent lodging, and so I just booked Tramlines, which was around £230 for my ticket and 3 nights hostel lodging.
The insurance won't get you a refund because you want a different campsite, it's only if illness or an accident prevents you attending - https://customer-support.seetickets.ch/portal/en/kb/articles/ticketprotection#:~:text=Ticket protection from Allianz Assistance,against theft at the event.