Donate the £ you'd spend on favors to a charity which may mean something to somebody attending your wedding or that means somethig to yourselves.
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That's what we did. I think favours are totally optional. Personally, as a guest, I've never kept them as a memento or anything like that. I find them a bit silly and a significant extra bit of expense and fuss for the bride and groom to be bothered with.
If you like them, go ahead, but you can make the same gesture to your guests with a donation and it does some good rather than just create a lot of fuss and waste.