I've also just purchased an 18 month old Cherry Red TH. Loving it so far, I didn't realise it was such a rarity here.
My assumption is, regarding TH no longer be available on the UK configurator, that it's just not viable for the UK market. At the price point they sell for, if a person wants increased off road capacity they'll go for a Wrangler, if they want all the comfort they'll go for a Grand Cherokee. Combine that with the new tax laws here that will make vehicles just over the £40k mark undesirable and so few models already being sold, you can understand why they've gone that route.
Really pleased with mine though and looking forward to having it for many years to come.