You will find that the CAA are very tolerant and patient over this issue. Even if you cannot meet the required JAA hearing frequency test levels, the next step is a practical hearing test (could be in a sim) to assess you ACTUAL ability to hear in your true working environment. The CAA's attitude is one of - can this person still do their job safely - can't get much fairer than that.
BA unfortunately does appear to want to impose more stringent limits on its staff as a company whereas most other companies leave this sort of area to the CAA.
I tell you all this from my own personal experience.