The leaves will probably benefit most of your plants,Sally. Just check none of them are being swamped so that they cannot breathe while they still have leaves on. When perennials have retreated underground the layer of litter on top will keep them safe from frost damage. I am 83 and have a large garden with mature trees - willow,oak, pine, eucalyptus, tulip tree, gingko biloba, Indian bean tree,nut trees, huge apple ,pear and plum trees, and the only thing I do is dig out seedling trees in the spring. I've learnt how to cope from the Botanic Garden which has very mature, wonderful trees all round the site,but still mulches with leaf mould, shredded bark etc. to save the roots from harm in harsh winters.