Oh dear got pregnant and can't afford time off work?

I live with my partner and we weren't trying - in fact we were using protection properly and well somehow we are expecting a baby. The house is big enough for a baby but we are on a very, very tight budget and we would not be able to afford our mortgage repayments if either of us took time off work and we cannot afford nursary even with the childcare voucher scheme. Our mortgage is fixed for the next two and a half years and there are unaffordable early re-payment charges so we cannot switch to a longer term one till then. Do you see the pickle I am in?! I can afford to take the six weeks' maturnity pay on 90% salary but not the rest (I live in the UK). My mother lives locally and always said when I had kids she would care for them during the day whilst I worked. Just how bad is it leaving a very young baby with grandma all day whilst I work - I mean there really is nothing else I can do except the A word and I really don't want that.