First of all, congratulations on not just rushing into it, you are obviously planning for it and realise just what a commitment it is.
I suppose first of all you could think whether to get a pup or an older dog. There are advantages to both. An older dog will usually come already spayed/neutered, housetrained and will have gone through all the puppy things like running off with your slippers!
A puppy needs to be trained how to do everything - where to wee, where to sleep, what it can/can't chew, what it can/can't bite, how to walk on the lead, sit, stay etc. Teaching your pup all of this can be a challenge but huge fun - it just depends on what would fit in best with your lifestyle.
Next thing to decide is whether you want to take a dog from rescue (and there are lots of them all round the country) or buy a dog from a specifc breeder. There are arguments for and against each, and often people get heated over it, but at the end of the day it is an individual decision for you to make.
As for which breed, cross etc to get, that is the hardest bit to decide probably :) I have had many dogs and now prefer dogs that are neither too big or too small.
I am the proud owner of a cockapoo, a cracking little dog, full of love and fun, great with kids, thinks everything on four legs is his playmate and every human a friend for life. I would recommend them wholeheartedly, but have also had other dogs, crosses and mongrels that were lovely as well.
If you are interested in a cockapoo, here is a little bit of info on them. Good luck with whatever decision you make :)
www.cockapoo-owners-club.org.uk/