Your neighbours were mis-informed. A property can only be revalued for Council Tax if a sale takes place, you're safe all the time you own it but when you sell up the new owners might get a unwelcome surprise.
Good luck. I hope West Sussex CC are better than Kent CC, I looked at doing the same last year, put off by an application fee of £350. I could have chosen any contractor I wanted but they had to meet certain criteria which ultimately meant it wasn't going to be a cheap or even moderately priced...