Been signed off work for two weeks. What shall I do??

Go back to your doctor and ask to be referred to a counsellor. Talking through the trauma of 7/7 and its effects on you will definately help. You need a short course of Counselling sounds like you have post traumatic stress disorder and your anxiety is totally justified. If you can afford a counsellor go to the BACP website and get one that specialises in short term trauma work. As it is effecting your ability to work why not try your human resources dept and as they have a duty of care to you they should be able to meet some of maybe all of the costs. Be well.