On the scent...

An admirable idea for you. I have done this for the past six years since my issues manifested. Sadly I gave up annuals unless they are in a pot. Evergreens are essential, especially if they flower and are scented. Mostly they need little maintenance. You can even do lots of edibles in pots.

Because I cannot advise you because of my location and climate, but I am sure there are folk on here who can.

I hope you are doing well and look forward to seeing what you do.

 

I have lots of shrubs and trees which means, with a mulch of bark and chippings, the upkeep is not that difficult, mostly winter pruning.
I'm not really into scent but I do like unusual foliage shapes and flowers.
Some blue bells and primroses under the shrubs always look good in spring, Hardy cyclamen are good also.
Eucalyptus can very quickly get away from you, mine grows new shoots 8ft long each season.
You could try Camellias if you soil is neutral to acidic.

 

I agree, but miss one year, and before you know it, its almost a tree surgeon job.
Mine went adult even though I was pruning every year.

I think there smaller ones, but often they are not totally hardy.

 

If you want a scented shrub for winter try Mahonia 'Soft Caress' ... Their leaves are not spikey like the usual Mahonias and they only grow 3 - 4 ft so don't need any maintenance. I'm going to get one from Farmyard Nurseries in the new year. They are £11.99 for 2 L size pot.
Farmyard Nurseries are based in Carmarthenshire but you can send for them by mail order or whatever it's called.

 

Agree, avoid Eucalyptus, they look so nice when newly planted but in no time they become a massive thug that needs the chain saw gang each year to keep it in check.

Not something to be planted near the house either .

 

Here are a couple more suggestions for easy, scented evergreens...Eleagnus ebbingeii or it's yellow-variegated variety 'Limelight'. You'll hardly see the flowers in Sept/Oct but the perfume is beautiful, then followed by pretty silvery-pink berries. And Pittosporum tobira. There are plain green, variegated and dwarf forms of this shrub. Again, not showy flowers but lovely scent.
ETA: Most Philadelphus (Mock Orange) are scented but 'Virginal' which is widely available, isn't. Avoid. Anything with coronaria in it's name will be scented.

 

No need to rule out Eucalyptus if you want one they are a few small variety's like French Blue ( 8ft ) and baby blue ( 10ft ish )they is another one but its slipped my mind .

I like the scent of Choyisa and they are dead easy to grow and maintain . Roses aren't particularly low maintenance, they can if left be but it will probably look a tangle mess and you may not get the best out of them . Not to put you off roses I love my shrub roses wouldn't be without them.

Personally FC I'd be looking at multi seasonally plants / evergreens and a good few really reliable plants like hydrangeas paniculata - phlox are great and with scent , if I remember right your garden isn't the biggest . Plants like Cornus siberica variegata Alba have lots of interest throughout the season nearly all the Cornus are brilliant in my opinion , Rhododendron ponitcum varigated evergreen / interesting foliage flowers or goldmine is a small version . Abelia are good plants as well . Noisette were asking about a Parrotia persain spire I am growing has multiple interest it be a small upright tree eventually .

Michael has mentioned a nice plant Mahonia soft caress , soft caress is a summer flowering variety . They is another exact same foliage but flowers in the winter called Sweet winter .

 

I was going on information given to me by a friend who grows it, but after looking it up it seems to flower late summer to autumn.
If Sweet Winter is better then I shall get that one instead. Thanks @Perki.

 

Mahonia soft caress is nice and I'm only just hearing about sweet winter....get them both!
Add hebe to the list. The small leaved varieties are more compact and require less maintenance, I have twenty odd types and there is one for most aspects in the garden, alas, not scented.
Helichrysum italicum and rosemarinus officinalis plus lavendula varieties will add scent if you get touchy feely with them

 

Not guilty M'lud That was Caroline, but I'm tempted too.....