The HTC Hero has appeared on Orange UK's website, however it currently wears a teasing "coming soon" badge. According to Orange, the pricing information should be available tomorrow, but you can definitely expect the free-on-plan option among others. T-Mobile is also expected to release the device shortly after under a different name, probably G1 Touch, also fully subsidized.
P.S. If you want the white version of the handset, you're out of luck in these cases - both carriers will offer the graphite edition.