###Sun hat
I highly recommend a sun hat of some sort.
I currently have a cheap and cheerful hat I bought from [Amazon UK](http://www.amazon.co.uk/gp/product/B000EBI3L8/ref=wms_ohs_product_?ie=UTF8), but pretty much anything that keeps the sun off your face will help to keep you cool, while also reducing the appearance of aging and the probability of skin cancer.
Also keeps rain off if the weather takes a sudden turn for the worse (I did mention that I live in the UK, right?) ;)