Need help with wild flower garden.

I have a space in front of my cottage about 2/3 meters by 4/5 meters. It has lots of blue bells and forgetmenots as well as a few tulips.
It also has things called ''golden rods'' or ''golden rockets'' and lots of ground elder.
The ground elder and rods rocket things have completely taken over. The garden had stood unattended for several years.

Today I took a digging fork to it and took all the rubbish out of it , as well as 30 litres of bulbs which I intend to put back.

What I want is a wild flower bed that will give me flowers all year round if that is possible, I love the blue bells and forgetmenots but they dont last forever.

Can anybody recommend a way to have different flowers with the seasons? I would like to keep it cottagy and colourful. Do I put grass down as well? I am a complete novice at this.

This is how it looked before I took the digging fork to it.