just thought if a new owner genuinley didn't know it was an aftermarket exhaust. Like on your run of the mill car, if your exhaust fell off, and you went to kwik fit or summat and they put on a new, slightly better exhaust you wouldn't tell your insurance would you? Notice that a lot of "standard" valvers, specially on ebay, are selling with s/s exhausts and not even listing it as a mod.
Know what you mean about any excuse though... may ring up see how much it would cost