On topic, a lot of it came from british expat:
Make sure you have at least a year left on your passports.
Dig out all your personal paperwork, including birth, adoption and marriage certificates, employment refeences, driving licences and qualifications.
Update your CV to make it suitable for the Oz/Kiwi market place.
Start job hunting.
Put your house on the market.
Get your finances in order, consolidate bank accounts and reduce debts.
Consider talking to your employer about your migration plans.
Talk to your childrens schools about your plans and ask them to prepare hand-over files.
Discuss your plans with extended family and friends.
Get quotes from removals companies and flights and get them booked.
If you are shipping pets, make sure they are fully innoculated and fir to travel. Your vet can advise you.
Get quotes and book pet shipment.
Sell any unwanted items of furniture and clear out cupboards.
Clean and paint any garden tools and furniture you plan to take. Items with soil on will be denied entry at customs.
Give formal notice to your employer
Ask your doctor, dentist,optician for your hand-over files.
Open an Oz/Kiwi bank account.
Request credit references from your bank,building society or any other lending agent.
Identify temporary accommodation in case your house sells sooner than expected and you have to move out
Make sure passport is stamped for CFO
Make sure visa stamping has enough time
Track down temporary accommodation in Oz/NZ.
Book accommodation for each destination on route.
Register children in new schools.
Book accommodation in OZ/NZ for pets.
Start having Goodbye parties now as time runs away at the end.
Organise all birthday cards and presents for the next 3 months.
Request up to date statements on any endowments, pensions and investments.
Depending on your tenancy agreement, give notice to your landlord if renting your property.
Give your change of address to your bank, passport office, DVLA, pension company, inland revenue, insurance brokers and accountants.
Bring council tax and utilities up to date and cancel accounts for TV, internet, phone and insurance.
sell any items you don't want to take with you, or donate them to a charity shop.
Arrange all your post to be redirected to a friend or relative.
Transfer funds to Oz/NZ.
Start packing non essential items.
Collect all hand-over files from doctor, dentist, optician, schools etc.
Arrange some private health cover for Oz/NZ if required.
Pay off any outstanding debts.
Close any surplus bank accounts and destroy unwanted cards.
Shred any personal records you are not taking and dispose of.
Confirm the removalists are booked.
Ensure all your relevant paperwork is in a handy travel file.
Cancel any redundant direct debits or standing orders.
Ask for a copy of your No Claims Bonus from your insurance company.
Cancel any newspapers or satellite TV subscriptions.
Sell your car, bike, van or any other transport you wont be needing.
Cancel car insurance.
Buy some currency for each destination on route to Oz/NZ.
Throw more Goodbye parties!
Ensure that your gods are either about to leave the UK or are on their way Down Under.
Organise any presents and cards your children may want to send to their friends prior to leaving.
Make sure transport to the airport is organised and will arrive in plenty of time for the flight.
Establish who will be coming to the airport to say goodbye.
Pack activity sets and small gifts to amuse young children on the flight.
Get a good night's sleep