Because of its scarcity, I'd need to see pictures before I'd venture a guess on a value. An early signature (1982 and earlier) with an all-around VG rating could fetch >$5K to a serious collector. But a signature from the 2000s won't command as much IMO. But let's face it, there are just not many 1st edition UK Carrie books in circulation so pictures are needed to help narrow down a price.
John