Clearing a border

[PattWV6]

I want to change a border in the front garden from a neglected perennial patch into something contemporary with architectural plants. What is the best way to make sure there are no residual lurkers waiting to ruin my design? Will I have to dig out all the soil and replace or is there a way to kill everything then replant? I'm on a budget and can't justify hiring a skip
To remove the soil so may need to put it down my trousers and shake it out when I go for a walk ;)
Current border has a lot of forget me nots, geranium and spring bulbs in plus random perennials.
Thanks.

Just dig out the plants, including all the roots, and add lots of organic matter to improve the soil.

You will always get lurkers... Whether weeds or perennials that are popping up. You just need to keep removing them and they will eventually vanish permanently!

I would think carefully about your border's design. You are likely to want some ground cover and some perennials alongside more architectural things. Sometimes you can reuse cottage garden plants in a very modern way. A great example might be the perennial planting by Piet Oudolf at Scampston.

What are you planning to do with the bulbs and plants? If you're not reusing them and a near me ill happily take them off your hands! If not I'm sure someone on Gumtree etc would have them -hate to think of healthy plants being killed!