Zarch wrote:
Can anyone recommend any other these and/or anything that i should
investigate?

I've no more room, so I use lots of pots that I move around now ...!
But in the grasses I have alliums, lots of different ones - some are
sensitive to depth so make sure you plant at the right depth; I use
crocosmia to bring bold red colours where it's a bit dark (I like tall
flowers).

Is my theory of getting all year round splashes of colour a valid one?

Sure, but you can also achieve this with wild flowers and perenials,
like you already have. Lychnis, the rose campion one has an amazing
colour and self seed. Perhaps that's what you should look into. If they
seed where you don't want, just move them. I've found my garden growing
by itself in this way and giving me splashes of colours by itself )