Hi Lisa,
You could try looking on your local council website.
I was CRB checked 4 times in 2 years when I first moved up here as I used to work as a teaching asstistant but I was only voluntary so to raise some money I used to work as a dinner lady and although I had already been CRB checked to work in the class I had to be CRB checked again even though it was the same school because it was 7mths old, then about 9mths later I was an exam envigilator at the local secondary school and they CRB checked me too.
So although getting CRB checked yourself seems like a good idea from my experience if your CRB is over 6mths old it won't mean much.
I wouldnt mind but im probably one of the most honest people you'll ever meet lol.