He's drunk normally since then, no more tray related problems.
Funny story though - while we were at boyfriend's Dylan kept trying to attack the washing machine when it was on wanting it to stop

and when I took him out on his harness this morning he tried making friends with a spiky plany that was at the edge of the garden from next door both sides

came as a surprise to him when the spiky plant spiked him
Should I still mention his tray to the vet when he goes in later on this month or would it be OK to leave if I continue to monitor him?