We moved last October, and I was nervous of using a packing service because I'd have to find everything again on the other side!! We moved three weeks after I'd had a baby, so spent the last stages of pregnancy furiously packing.
We started with the loft - brought everything down, packed into boxes or took stuff to tip/charity/recycling... Then worked through the house starting with the stuff you don't really 'need' like books, CDs etc, and lots of clothes, children's toys...
I had a small notebook in which I kept a record of each box I packed. I.e. the number of the box (write on the top and the side, because if the boxes end up stacked in your garage on top of each other for the next 12 months, you can't see the numbers on the top of the boxes and have to keep re-arrangingthe stacks) and a summary of the contents. I didn't itemise each thing, but if something important was going into the box that I knew I'd need to find, I wrote that in the book, otherwise just a general summary (bedding from nursery, child x's toys etc). I found the book invaluable for locating items - we're still unpacking, we had 209 boxes (just checked the book!).
Do you have any camping friends who could lend you a portable fridge for the move? We unplugged our fridge/freezer the day before the move, but were able to keep e.g. milk, butter etc to hand in the camping fridge, and plugged it in when we got to the new house.
I aimed to pack around 5 boxes a day - more than that was a bonus. Obviously this entails sorting, throwing stuff out etc, so not just a case of putting stuff straight into the box.
If you have a shed/garage/outbuilding etc, tackle this early on - you probably won't need much of the stuff, and you can forget how much there is - you'll feel loads better once that is all sorted.
Many removal companies won't carry e.g. paints/chemicals etc so we took a few plastic lidded crates of those around to a local friend who kept them in their garage for us.
Children can manage with surprisingly few toys, so pack them!! We found they took lots of boxes because one large item e.g. Fisher Price garage, playmobil school house etc took up much of a box.
Invest in one of those tape dispenser things e.g. from Staples. They only cost a few quid, but really do make the packing process quicker. And some sharpie markers to write on the tape.
We reached a point about a month before the move where we thought the house was looking quite sparse, and felt we were really making progress, but the last lot of stuff was the hardest to sort/pack/do without... I have nightmares about those last few weeks, particularly as the moving date had moved twice, and we had a newborn, plus three other children under the age of 5!! It can be done though. Good luck!