The undertakers in our area normally provide a collection box with a printed note to say which charity is benefiting from donations. (Since Covid, some set up an electronic means to donate on a memorial website.)
But yes - I've was surprised to find coppers and other small change in the collection box when handed the collection box by the undertaker. I rounded it up to a decent amount myself and sent a cheque to the charity.
My husband's funeral was during Covid and had restricted numbers as a result. I think that the death notice simply asked for people to send donations to a particular charity. This time round, I didn't collate any of it and simply sent a decently sized online donation in memory of my husband.
ETA I've somehow lost half my post. I'd also said that our local crem doesn't have space for a large number of floral tributes - you can only get so many on and around the coffin.
DH had the family spray, a wreath from his regiment and his regimental beret.
After the service, the crematorium staff returns any items such as the beret and places the floral tributes inside a fenced area. I've actually just remembered that I was asked whether I wanted to take the flowers away with me, but declined.
So far as I'm aware, they're only there until the funerals the following day - so there's no point in non-family flowers. It's different for cemetery funerals.