I was sure it wasn't but I think its basically down to watering and my lack
of it.
But now that its grown back the leaf size has increased

As long as it's alive, don't worry. At your latitude, remember that even though
it is still warm, you have several hours less of daylight now than you did in
June. Also, new growth will tend to have larger leaves than older mature
growth. As the tree stabilizes, the leaf size will tend to get smaller. Don't
try to reduce leaf size now until the tree is healthy.
Iris,
Central NY, Zone 5a, Sunset Zone 40
"If we see light at the end of the tunnel, It's the light of the oncoming
train."
Robert Lowell (1917-1977)