Planted end of may, already looking a bit sad. Does it just need more water?
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It may have suffered a bit of drought, but the principle damage to leaf edges and tips, that frazzled appearance, is likely because it's in a sunny spot. Whilst japanese Acers don't mind sunlight, they do not appreciate full sun in the middle of the day when temperatures are high. I can't help thinking it must have also suffered from windy conditions, because there has been plenty of strong wind here in London during the last few weeks, so even if it's not in a particularly windy spot, it will have been exposed to some wind.
You might just examine all the woody parts to make sure there is no scale infestation or any other problem on the backs of leaves; if not, it's environmental.