I'd pinged an email to Lee to see if they had any suggestions when I first discovered the problem and they use 3M 300LSE double sided tape. Great that they're happy to help out in supporting older Lee items, I just wish the shop I'd bought the hood from was as supportive. I've only bought from them twice and twice I've had faulty products that couldn't possibly have been their fault, let's just say I can't aFford to buy from them again.
Thanks for all the help though folks, very much appreciated! Just need to decide which method to go for, and hopefully don't have to follow up with "I've ruined a Lee wide angle hood....".