b4 you buy. get some break cleaner and drop your isv in it (fully submerge) give it a wash out then pull it out and leave it 10 - 15 mins and try it. should do the trick as the only block up normally unless its broken but its worth a try.
£20 is about right if delivery is included. if its from a scrap yard haggle and fit it there b4 you pay so you it works.