Perennials

jamesabcdef

I planted a beautiful cottage garden this year (first time) with about 70 perennials. I dead headed them quite conscientiously in mid to late summer, but have done nothing since. I'm aware that I should check which ones are vulnerable to frost and deal with that. But should I now do the other work that I should have done in the autumn, e.g., dead-heading and cutting down to ground level etc as appropriate, or should I leave it till some other time? James.

K67

Your choice. If they are looking tatty cut them down but if they have interesting shapes or seed heads I would leave them until spring. 
If you have slightly tender ones like penstemon it's best to leave them as the top growth does give some protection .
Of course if you have any still in flower obviously leave those. 
If you want advice on specific plants ask away but its best to limit it to 2 or 3 at a time.
And finally welcome to the forum 

Posy

Hello, James, and welcome. One thing you can do is spread a nice mulch of well rotted compost (not potting compost) around your plants to protect them and give them a boost in spring.

Fairygirl

Hi @jamesabcdef - as the others have said - it's hard to be specific, and it will depend on your climate and the plants you're growing. Anything borderline in hardiness terms is better left with a bit of foliage for protection, but many plants can look very tatty at this time of year, so sometimes it can be down to aesthetics . 
I cut back anything that looks really rough, but if I think it might be a bit on the edge of being totally hardy, I leave some stalks. Anything that's not completely reliable would be lifted. 
I don't grow much that can't cope with my climate though, which makes it easier, and sometimes you need to experiment a little   

KeenOnGreen

We don't grow anything non-hardy in the ground any more.  We grow those in pots, so they can be put in the greenhouse over Winter, makes life much easier.  Our personal preference is to do any moving and tidying up of perennials in late Autumn, although we leave the spent flowerheads on many plants for the birds.  That way when Spring arrives, we have almost no work to do, other than just watch and enjoy.  Some people prefer to cut back/divide, etc in Spring, it's all down to personal choice.