Iv just figured it out myself i do have data. I got confused with it saying 0.0mb but iv just done another text to see what i have left and seen a difference in the texts.
This morning it said this
1 of 2: O2: Hello. You've got Unlimited text and minutes and 2379.7 MB of data left in your Big Bundle. Make sure you use them before 14 Apr.
2 of 2: O2: You've got 0.0 MB of web data from your offer allowance left to use in the UK until 13 Apr at 11:59pm
Then just now it says
1 of 2: O2: Hello. You've got Unlimited text and minutes and 2037.8 MB of data left in your Big Bundle. Make sure you use them before 14 Apr.
2 of 2: O2: You've got 0.0 MB of web data from your offer allowance left to use in the UK until 13 Apr at 11:59pm
After looking at them both i can see that its gone from 2379mb to 2037mb so i dont know why in the second message it says 0.0mb but im presuming that the first message is telling me i still have data. I was listening to were it said 0.0mb so thought i had no data