The HTC Sensation is now available on Vodafone UK, from 20th May onwards. Customers who pre-ordered the device should be getting their devices very soon.
The Sensation is available for free on all Vodafone plans of 35 GBP or more per month. There are plenty of plans and packages available. Although for the 25 and 30 GBP a month plans, you will have to pay 199 and 99 GBP respectively for the phone.
Vodafone has the phone exclusively for the month of May just like Phone4U had a head start with the Galaxy S II.
Other operators will receive their units in June. You should also be able to buy unlocked Sensation handsets for around 500 GBP in June.