Any of the Sedums would grow well with lavender, also Asters and Gazanias would look nice.

Thank you! I will look them up :-)

Asters would be ok but gazanias need a sunny spot otherwise they wont open. I would suggest galliards or coreopsis. Both are yellow and would compliment the blue lavender. Or for a cheap annual you cant beat marigolds.

I would add some cream or pale yellow ones rather than go for all bright yellow with lavender. Have a look at agryanthemum. Perhaps some white and some pale pink penstemons behind the lavender too?

That's why I suggested Gazanias Thecat, it is in full sun. Galliards and Coreopsis start looking gangly and floppy.

I'd go for white or pale pink, something tall and airy like Gaura or thalictrum.

My Sedums are taller than the dwarf Lavender 'hedge' but on the other side of the path so dont swamp them.
Best check the height of these plants before buying them.

Good thinking Diane - different varieties of lavender grow to different heights too.

Thank you to everyone for all the suggestions, I did get some gazania's which look lovely, and will try some of the other intertwined whilst the lavender gets going. Maybe on the corners I'll put something a little higher to add some additional interest.

As I said, I'm new to gardening, so all suggestions are welcome - no doubt I will have some trial and errors!

You all seem a wonderful font of knowledge, so watch out for more questions!!! :-)