hi there i have a 1995 m reg discovery tdi with the oval/single button remote key fob which has started to play up sometimes it will lock/unlock and sometimes it wont i have changed the battery but has made no difference can i buy a used key fob (the ones found on ebay) and have it programmed to work on my discovery or do i have to buy new any help would be great as it takes a while to unlock or lock at the minute and is a right pain in the ar** if its raining thanks chris 