point one:

ask the person who is being visited for their visitors to park more consideratly

if this fails to work, proceed to step 2

call the council and tell them that local parking is becoming difficult as commuters are using your street to park on and then they fuck off to town and block up all the parking spots, you may get them putting in parking bays with controlled parking, which you will have to pay for by way of a residents permit

if all this fails, plan c

park YOUR car in the neighbours spot and then get the wife to park in YOUR spot in such a way that you can only get 2 cars in instead of 3

just make sure that you both have a week off as holiday and then don't move the cars, or get some mates to lend you a car for a few days or whatever you need to do

obviously this is going to cause a few issues for you as to where you park YOUR crs, but this may be just enough to convince the neighbour to see sense

option the next is just pay some junkies to brake fluid the car with the words "don't park here you fat cunt" or words to that effect

hth