i noticed they are doing some very good deals is any one with them are they any good and whats there data speeds like also where is there call center

http://www.virginmobile.com/vm/paymonthlySimOnly.do

Virgin use t-mobile network with orange as a backup. I believe speeds are capped at 3.5mb. TBH, i've found it fast enough to stream video and play online games and they don't seem to care about tethering

whats the data speeds like compare to 02/giffgaff as i am with them now and the data is really slow.

Virgin Mobile DL speeds are capped around 1.8mb. Whilst you might get slightly higher speeds with O2 . You will almost certainly get far better 3G coverage with Virgin.