What is said above…
A bit of voluntary work shows that you know what the realities of work in this sector is all about, it is hard and physical. Will act as a great reference too…
Second, there is quite a dark art to putting a decent application together, so give yourself time and make sure you can justify all the person spec. As a trainee they will want you to be willing, keen and wanting to learn so try and get this across.
If you are unsuccessful and honnestly want to get into this work then what about looking at a Full Time Vol position with the National Trust. A lot will offer accom and some form of training budget. Although you will have to be able to financially support yourself one way or the other.
Oh and the hours are all over the place and the pay is poor but there is no better work on this earth.