10% is usual. usually at the nurseries on the hospital sites or near to the sites. never seen anything that would be a substantial discount.
you'll get to apply for childcare vouchers as salary sacrifice (each of you up to £243 per month, its taken before tax and ni deductions)
The NHS have specific childcare specialists within the children's information services. I would phone your DH's HR and ask for the contact details for this person. You can then receive all the info they produce and find out whats on offer.
in our local trust we get a monthly email called "family matters" which is a monthly mag full of info, even study, info days to attend pre and post maternity leave regards finances, credits, childcare options. Ask DH if he gets something similar and ask him to forward to you.