My arum lilies are outside and about 4ft high and about the same width they are healthy producing 70 plus flowers on each bush how can I make them a bit smaller they are the talk of the neighbourhood but beginning to take over

You can divide the clumps but wait until the Autumn.
If you end up with too many you can give the spares away - put them on Freecycle if nobody you know wants them. If you need tips on how to divide them ask on here again around October.

I'm not sure what you mean. You want to make your arum lilies 'smaller'? They sound fantastic. You can divide the lot, but I'd wait until they finish blooming. If you want them shorter, you need to choose another cultivar.

Divide them up, as Stera says and then your neighbour's will be able to have some too.