You need to do a business plan. This is vital to secure any funding needed to set up your business. As you are unemployed, you may qualify for a grant from the job centre. To get a grant you need a really good business plan.
Lots of information online about doing a plan, and you can get new business starter packs from banks that tell you how to do a plan.
What you need to know:
Who are your customers?
Who are your competitors?
What are your competitors offering?
What can you offer that is different?
How much will you charge?
How many customers will you need to make enough money each week?
Where will you get your customers from? Advertising? Word of mouth? Leaflet drops?
How much will it cost to get all the equipment you need to get up and running?
What experience do you have in Valet business?
These are just a few questions you need to answer. There are many more, and you could seek advice from businesslink . gov.uk
More than happy to offer any help I can, always pleased to help someone who wants to help themselves. I am good at finance, not good at Valeting
Good luck mate.