Very novice gardener here...please speak slowly 
I have a lovely bed (inherited from the very green-fingered people who previously owned our house) but it has developed a sparse patch.
It's not a problem, but I'd like to fill it in with something nice and I'm not sure what's appropriate. The bed gets sun all day and the soil is quite dry.
Any ideas? Have included some pictures to hopefully give an idea of size and surroundings.
Thanks in advance.