According to the govt website you do not need a solicitor but it "can be useful if you have complicated personal, property or financial affairs."
What is a Lasting Power of Attorney? : Directgov - Government, citizens and rights
You can download the forms from this link
Making and registering a Lasting Power of Attorney : Directgov - Government, citizens and rights
And this link tells you about the fees - £130 for each of the two types of LPA, financial and property and health and welfare.
Lasting Power of Attorney - what it costs : Directgov - Government, citizens and rights