No harm in trying? They have a hearing test at medical and I remember not being able to hear a bloody thing and I still got through. Just go for it man. If you wear a hearing aid then it's a no, all you can do is go along to the medical and the Army will test if you're suitable. If you're not, well the Army paid for you to travel (If you go buy train) to have a free full body touch up, I mean health check. They also provide you with lunch.
I rejoined the Reserves following Regular service having lost the hearing in my left ear through gunfire. (and recieve a War pension for it) Albeit it is actually a specialist unit requiring civilian skills that doesn't require perfect hearing, I had a good CO that managed to convince the right people. I have subsequently done numerous tours with no problem. If you have previous Nursing experience it might be worth being honest and speaking to the right Bod.
In some case you may have to have more regular hearing checks to check that is not getting worse.