browning at leaf tips is often a sign of wind burn. is it in a particularly windy spot? or is it dry? one of mine in a pot gets very dry as it is in the shelter of a wall and rarely gets rained on. hope this helps.

Lots of possible reasons. Japanese acers do not like a windy spot, full sun, not getting enough water, being in alkaline soil. As you don't say where you are in the UK any or all of these could apply to your acer.

If it is in a windy spot or full sun wait until autumn and then move. If your soil is alkaline you will need to add ericaceous compost, which will be easy to do if you need to move. Lack of water is unlikely right now in most parts of the UK but the tree could have been stressed earlier in the year in you live in the area where there was a long drought. Of course if you only planted the acer this year it will need regular watering even if it rains.