The hair clippers on sale in Boots the Chemist and other electrical goods shops sell these hair clippers along with combs set at various lengths 12mm, 18mm, 25mm and other measurements that can be affixed to the clippers very easily and they take virtually no skill to attach or use.
Once you have chosen the length comb you're happy with start clipping away all over your head from every angle you can think of with that comb, of the appropriate length, you've chosen attached to your clippers until you can hear and see the clippers are no longer cutting any more hair from your head you're done.
All you need now is to take the comb off of the clippers and then sit down on a convenient chair and get a trusted friend to trim all around the back of your head for you with the now, combless clippers, all the bits you can't get to.
These clippers my ones are Remington's clippers from Boots and the combs I've been referring to come with the clippers and when you see them it becomes obvious how to attach them, they're quiet simple to use, I've cut my own hair for years and have obviously set the trend in hair style around here for years too, my wife does all of the trimming for me after I've done my top knot.
I must check where my shares in Remington are at the moment.
Seriously I go for a short all over nice and tidy and doesn't dangle in the eyes haircut, why pay, I don't know know, say £20 when you can buy a pair of these clippers for somewhere around £10 to £15 and after two or three haircuts you've got your money back, no sitting around waiting your turn.
Hope this is a help for some of you and all the best, ippy.