normally a credit reference check like the ones a bank does for a loan is done as part of the check still though you did used to have to give permission for them to see your bank details too this is no longer the case
BUT it would still be possible for them to check that if they so wished as part of the enhanced version anyway
you can see what you have to fill in here
http://www.crb.gov.uk/pdf/crb11%20guidance.pdf
just finishing mine off at the moment just got to find where the wifes hidden the marriage certificate now lol