There are various options for the original iPhone 4 at Tesco, but the one I’ve somewhat randomly chosen is £130 up front for the 8GB model, and £20PM for 24 months. That’s £610 total.
The monthly allowance is pretty generous, with 250 minutes, a whopping 5,000 texts (167 per day in a 30-day month), and 1GB of data.
Again, this is the original iPhone 4, so no Siri. Ahem.
(Thanks to Greg Thomson at HUKD)