There is no set format for a will.
With professionally drawn wills a lot depends on the individual style, of the draftsman. The important thing is that the terms used are unambiguous so as to avoid costly disputes after your death. There is also no requirement for a will to be written on any special type of paper.
Like a cheque it can be written on anything.
For example, the London Probate Registry has a will written on an egg. However, it is not recommended that you adopt the procedure of writing on anything other than paper or see http://www.itc.co.uk/howtomakeawill
The law's requirements for a valid will are not particularly onerous.
1. The will must be in writing.
2. The document must be testamentary; that is, it is intended to take effect only on your death.
3. You must be of sound mind.
4. You must be 18 or over (21 or over before 2000).
5. The will must be executed correctly.
On the face of it, these requirements appear very easy to fulfil. In reality, there are numerous ways in which the writers of home-made wills manage to mess things up.
Sometimes they omit essential matters such as the appointment of executors or write conflicting dispositions of their assets.
Others simply fail to comply with the formalities of execution. I have dealt with one case where the testator wrote out the will in good style and had it witnessed by two witnesses.
Unfortunately, he completely forgot to sign it himself so, as far as the law was concerned, it was of no more consequence than his shopping list.