When making a big purchase go through www.topcashback.co.uk (same sort of deals as Quidco but no annual fee)
You've already started shopping on line which is great - so much cheaper. Tesco actually have a function that shows you the cheaper options, but just check the quantities aren't a lot smaller than you were buying before. Buy your fruit and veg loose. Package produce is £££ more!
Buy staples (rice, flour, pasta, cooking oil etc) in bulk and decant into storage jars (don't leave open packets in the cupboard or you could get moths or weevils - yuk!)
Don't be afraid to consoldate all of your credit cards into a single loan - just don't borrow more than you have as a debt. If you do need to take a little extra to get a better deal put the extra into a savings account to use in emergencies ONLY.
Start saving. Sounds mad, but if you and your DH each transfer £25 a month into a savings account on pay day then you'll have £600 to spend on xmas/birthdays. Also save for birthdays and holidays instead of sticking it on the credit card.
Cut up the credit cards.
Go shopping to the supermarket half an hour before closing (especially good on Mondays). They start heavily discounting anything that is going off the next day. Only get things you'll use - like mince/chicken etc but you can freeze it and then use it when you need it.
I think meal planning has been said and I'll second that cooking from scratch saves a fortune. Get rid of Sky/expensive mobile deals/gym memberships and change energy suppliers.
Can you remortgage to a cheaper deal? Lots of people leave their mortgages running and never check if they can get a better deal.
Shop around for home and motor insurance and use the cashback and comparison sites. And telecoms.
Ebay any unwanted bits or if you've got lots of childrens toys/clothes you don't need any more you could get a table at your local NCT Nearly New sale. Check the NCT website www.nct.org for details of upcoming sales.
If you have any savings use them to pay off debts so you can start from the best possible debt position.
We did all of that and managed to live off 60% of our previous income after I had DS.