As far as unlimited SIM tariffs go, Three's One Plan has always been pointed to as the best, however Virgin Media's managed to eclipse it today with its VIP package, which for £31 a month (or £26 if you're an existing customer) you get unlimited calls, texts, data, and for the first time for any network, free access to 0800 numbers.
It's not every 0800 number, mind, though calls to 0800, 0870, 0845 and 0808 are on the list. Added extras include inclusive insurance normally worth £8/month, plus a phone (nothing amazing is on the list, unfortunately.)
If you're not too concerned about premium numbers, its rolling 30-day SIM-only VIP tariff can be had for as little as £15 a month, for just the unlimited calls, texts and data.
Over to you, Three -- still think 2,000 minutes and 5,000 texts for £25 a month is impressive? [Virgin]