Posted: 05/04/2013 at 21:56
What's in front of the border at the moment? If it's lawn you can dig this up, pile it up somewhere upside down and cover it so it rots down (6 months or more) and you can then use it as top soil.
Your borders need to be as deep as possible - 3ft is good and 6ft! is even better. You will probably find your perennials flopping over the front in just 1ft borders.
As nutcutlet says it's not easy improving clay soil - I know as I've also got it and lots of compost, leaf mould, well-rotted manure and horticultural grit (which has been washed) helps a lot.