With regards perennial plants such as most of mine as I love cottage garden style like Lady's Mantle, I leave them to die down and then eventually tidy away the dead foliage as it only acts as places for snails to over-winter, which I don't want. Some I leave, thistles for example as I like the architectural look of them tinged with frost. Leave some wood piles for invertebrates to hide the winter away in and some dried leaves in areas for the hedgehogs. We have a hogitat and leaving dried leaves around it means that any hogs have cosy bedding for hibernation.
Time to give the lawn its last mow as once below 6 degrees it won't grow and also prune any bushes - I need to prune a red currant bush that is taking over. Also any trees which need reigning in, think about tree surgery service to thin out big trees and keep the neighbours happy and not in too much shade in the summer.
Divide any herbaceous perennials that have become thuggish, I have a few that have swamped borders like persicaria so I'll be splitting them and giving to friends - share your garden plants to save money. Another task for late autumn is to save any seeds thus being very frugal. In envelopes I store seeds such as verbena and hollyhocks ready to sow in the spring and I've saved money in the process.
Make some planters up for splashes of winter colour - heathers, pansies, ornamental cabbage, crysanthemums, skimmia and cyclamen. Purple seems to predominate at this time of year and I love how they look in galvanised metal tubs, very Scandinavian, All the aforementioned plants can be bought fairly inexpensively in bedding packs and make such a difference to a patio or at the front of your home for curb appeal.
The end of the year is also a good time to think about any hard landscaping. Whilst the garden is at its bare bones focus on putting paths in or laying patio areas, then it's all wonderful for spring.