Hi Louise and welcome to GoY. If you scroll down to the bottom of the page and click on the 'C' and the on 'Cottage Garden ideas' you will get lots of ideas and images for your own garden.

You could try annuals to start with to fill gaps, while the perennials are getting going. Some low growing annuals to grow easily from seed, which are also bright, are Poached Egg Plants - (Limnanthes), Nasturtiums and Godetia.

my top tip would be penstemons becos you can hardly go wrong, choose the less fussy ones and there is still a lovely array of colours and they flower reliably for ages.
Also stocks (or was it phlox?!) are lovely.

Heucheras have lovely bright leaves in different colours and many of them have attractive flowers too.

Basic rules of thumb for cottage gardens:

Informal and assymetrical designs.
Most cottage gardens face out to the street, often through some form of attractive countrified fence--ie. picket, rail, wattle, ornamental wire, etc.
In its purest form, on the house side of the front bed, there is a path and/or a narrow lawn, and often a foundation planting with flowering vines on ornamental trellises. Where the house is farther away from the street than the prototypical cottage, there can be a lawn with fruit or flowering trees, too.
They generally use plants with discernible character in leaf and bloom, not just blobs of color. Flowers commonly used for cutting are a traditional component.
"Innocent and exuberant" is the impression you are trying to make--usually they look quite full and crowded, and the art is in keeping them from looking weedy.
Mature cottage gardens are usually mostly herbaceous perennials, but a scattering of flowering trees, shrubs, and vines, plus annuals, biennials, bulbs, and even a few of the more attractive vegetables, are common companions.
Mostly, don't stress! Gardening is supposed to be fun and relaxing, and cottage gardens can provide the most of that. The best have been evolving for decades, so they are always works in progress, and any mistakes you make can be corrected.

That sounds like a very American cottage garden Tugb. I've seen all sorts of cottage gardens over here each one different, as the images on here show.

Make sure you have some 'simple' flower shapes such as daisies. The less intensely bred plants are more natural for a cottage garden and will encourage bees etc. Avoid any of the small, modern, mound forming annuals and go for looser things like Marigolds and poppies instead.

Good advice Volunteer...

that's interesting about what you term "mound-forming annuals" Volunteer. Please can you give a couple of examples?

Moon_Grower: Ayup! Kinda New England style. Actually, traditional American cottage gardens use more veggies and fruit trees than most European ones.

Yes, Weeding. By mound forming I really mean shapeless blobs of colour that the breeders seem to think that we want! An example would be the difference between the original Primroses that you find in the hedgerows compared with the type grown for 'spring bedding'. The flowers are very large and all merge together into one blob, rather than standing apart so you can see each flower! Just my personal preference! Each to their own, I suppose.

Thought-provoking thoughts Volunteer. Certainly the primroses/primulas commonly sold en masse for bedding lose their over-egged look very fast in a real garden. Proper primroses look beautiful year after year after year, more delicate.
And Tugb, I like a cottagey garden to have fruit trees and veg too, so much more useful than only flowers and shrubs and just as decorative.

True, Weeding. In fact, some of my customers won't plant anything that they can't eat!

Volunteer, the scary part is that the "blobs of color" actually are the best sellers in the nursery. Although few of those customers are what I would call gardeners, they apparently drive the industry. Many never do figure out why their gardens are so "ho-hum". : /

Yes, these are the same people who watch all the c**p programmes on TV, which makes the TV men think it's what we all want!! Still, unusual plants wouldn't be unusual if everyone grew them!!