Once you have obtained a Ltd Co., you will have to register it with the CIS people as a Contractor.
They will issue the Ltd Co with a UTR No.
To use the Ltd Co for agencies, you will need Public Liability insurance. How much insurance (1mil, 2mil etc.) The Ltd Co will need, will depend on the various Agencies.
For the Ltd Co to be paid by the Agencies, you will need the Companies House registration number, the LTD Co’s UTR No., the Ltd Co’s bank account details and a copy of the Ltd Co’s public liability insurance.
You can let the Ltd Co. employ you as an employee, or as a sub contractor.
In either event, the Ltd Co. will have to file end of year accounts with PAYE/CIS, Companies House and Corporation tax.
Depending on how you pay yourself, you will probably have to file a self assessment.
Tax will be deducted at source, unless you can persuade tha CIS people to allow the Ltd Co. to be paid gross (unlikely in the first year of trading).
You will have to ask for a form from the PAYE/CIS people to offset the deducted tax.
I believe Santander do a free business account, most of the other banks will start charging after 18 months or 2 years.