To stay inline with the rest of their price-plans, O2 is increasing the allowance of the cheapest £35 per-month tariff to 600 minutes and 500 text messages (up from 200 of each), and cutting the cost of the £55 down to £45 per-month.
They seem very good value now, especially as you get unlimited internet access and free WiFi at The Cloud hotspots. Might even be enough to tempt me away from T-Mobile.