Bikes looking good Adrian, I don't mid the plain look without decals, though I might just add a tubing sticker (Easily available) to break it up. If you decided to add Thorn decals at a later date I expect they're available. Did you save the headtube badge? I think I'd want at least that, so it had some badge, if you haven't got one, maybe Thorn could supply one.
I'm a bit jealous of those who've kept their bikes for so long, even bikes I've liked haven't always kept their place for more than a decade. Sometimes the desire for something different gets too much, though they haven't always been improvements that warranted the effort and expense.