oh yes, forgot hoodies (which I think look fine with cotton a-line skirts or shorts when running around after DCs) and breton tops. I bought them from H&M last year but I think they have changed the fabric supplier for them because they now bobble really quickly.
I also did a further mooch in the depths of my wardrobe and uncovered pale pink & coral skinnies and a pair of red chinos (really must not let on to DH...this is fast scuppering my new wardrobe plans!)
Jumpy - I wear my tunic with leggings and a cardigan on cooler days and have worn it by itself when on holiday in a warm country. Just remembered, however, that I have a nude full-length slip now so I will try that beneath to see if I can get more opportunities to wear it by itself.
Layering is key in this country and H&M do some great lightweight slubby long sleeve tees which I wear beneath my dresses or tops on cooler days. I have given up the hope for a long hot summer and have become far more realistic in my summer clothes shopping. I do, however, keep a small selection of "holiday" clothes which satisfy my need to have at least a few "wafting around a Greek island on a balmy evening" items in the wardrobe. I'm nothing if not an optimist :) Like Spooky I am never knowingly without a cotton scarf about my person. H&M do the best selection and they are very reasonably priced too.
So basically, I guess from the other responses we are looking at:
ankle skimming crops/rolled chinos - one neutral, one bright.
selection of vest tops & tees (long & short sleeve) & more structured tops
dresses: tunic style, tea dress, maxi etc
leggings
cardigans
hoody for more casual days
sandals
Having a colour palette is the way to go. I generally have navy/white/red with the odd bit of green in there but am going to try to go for more pastels this year: pink/yellow/blue/mint green.