To protect against the slugs and snails, I surround each plant with a good sprinkling of crushed egg shells.
Then I crunch them up by putting the shells in a plastic bag and standing on them (it is too painful to do it by hand!) I keep all the crushed shells in a container in the shed to use when required.
As you can see the hostas are relatively free from slug and snail damage.
To protect against the pigeons devouring my plants, I either use netting over the entire bed, or individual wire net collars that I place over each plant – they are just high enough to stop the birds!