ajoining propertys?

hi all,
my roof guttering is currently connected with the neighbours with half round pvcu pipe ,and there rain water and mine goes towards my downpipes,causing problems during even moderate rain,my problem is if i fit stop ends at the boundaries,will this not cause a problem for them when water reaches the stop and has no were to go?will i have to amend there gutters so the run goes to there down pipe?dont really want to have water running down the walls,of both propertys,is this a normal problem,as it looks like all the houses on the street have connecting roof gutters.if i fix mine would i have to fix theirs?

Their gutters will have a fall so the rain goes into your pipe. Stopping it with a stopend could cause problems especially if they have quite a big fall.

If their gutters are quite flat then you may get away with it, providing they have a downpipe on their side close by.

thanks,
sorry about the spelling