Where was this?

[Brainybri]

Are there any clues, based on other such photographs, where this was taken? It is either in Oswestry training camp or Prestatyn training camp. These are Somerset Light Infantry, sometime between 1917 and 1918. My grandfather (5th from left on back row) enlisted in January 1917 and was discharged January 1919. The sunflowers suggest this was not a winter photograph, so 1919 is out!