Havn't read all the replies, but I am now into 8th month of mat leave (I appreciate that I am very lucky) and SMP stops next month. I am not going back to work until September, so we have been "eeking" things out (neither of us is particullary well paid to start with, but I have fab flexi working).
1 - Stockplie groceries you KNOW you will need - loo roll, baked beans. Not baby stuff, until you know baby likes/fits/isn't sensitive to it.
2 - Ebay, Freecycle, Gumtree, MN For Sale/Wanted ads, MCT nearly new sales...
3 - Charity shops for clothes - I have a trip out to a local wealthy village, mooch round the charity shops and treat myslef to a cup of tea. On the bus. V cheap day out, and have bought most of DS's baby clothes that way.
4 - Don't skimp on a pram. We did, bought a second (5th?) hand travel system, it fell apart within a few months and we had to but a new one, new. Don't bother with a "Travel system". I used the ability to move DS in his car seat onto chassis for about 4 months. Then he got too heavy.
5 - We do lots of activities for free, through the SureStart Centre and HV does baby massage classes for first time mums. £2 for a course of 4!
6 - Mortgage holiday.
7 - Hide away credit cards.
8 - Use local baths for "Water Babies" (or whatever) rather than pricey private ones.
9 - I walked for miles and miles when DS was tiny - got me out, got me fit, kept him occupied.
10 - Check your council website for toy libraries.
11 - Many churches run Baby and Toddler groups for anywhere between 50p-£2 a session. NCT does local coffee mornings. I went to everything going when I DS was first born, and made lots of friends. Now we tend to go to each other's houses.
12 - Where we are all the buses have low floors, so I take the bus instead of the car if I am going into town. Saves petrol and parking money. And the hassle of getting DS in and out of the car.
13 - Library for books, DVDs etc. Ours does Storytime and Singsong sessions once a week. And don;t forget your Bookstart books!
14 - Join Lovefilm or something similar, and have all the DVDs you ever wanted delivered to your door.
15 - Eat a lot of pasta! Shop at Aldi/Lidl, or shop on line and don't get temepted by displays of spenny things in the shops. Also much easier than taking a baby supermarket shopping!
16 - Sell stuff the baby grows out of on Ebay, especially if you are sure it will be your only DC.
17 - Check all your direct debits etc and make sure there is nothing eroneous there. We got a few £100 back because we had been overpaying our gas bill.
18 - Befriend someone with a DC a few months younger than yours. Preferably the same sex!
19 - And someone with a teenage sister training to be a nursery nurse!
20 - My baby loves "Grobags" - but supermarket ones are far cheaper than branded ones.
21- There's nowt wrong with supermarked own label food. In fact we were already on that, and have downgraded to "Smartprice". Which is OK apart from peas and tuna!
HTH!
Good luck
One last thing - you will probably still care about potential debt, but apart from the baby, not a lot else!