Yes just checked their website and O2 does have traffic management even for unlimited user, but the restriction is not too heavy on unlimited user.
What's the real benifit for a real FTTP ISP ? BT infinity is in your list and I have just
done estimate with BT Infinity ,it's about 6.5 M to 8M, see below:
BT Total BroadbandYou can get our fast and reliable broadband with speeds of up to 8Mb. The speed prediction we have provided is an estimate, however download speeds can vary and the actual download speed will fall between a range. This is generally within 1-2 Mb higher or lower than your estimated speed quoted Between 6.5Mb and 8.0Mb.