The last time I did this I used this organisation who were fine
http://www.easyformations.net/
That was five years ago and the company still seems to be in existence, but I'm not specifically recommending them. I used the 'standard' package which seems to cost £70 now (it was £50 then).
You then need to get a business bank account using the Articles of Association.
Plus getting to grips with running the PAYE payroll (it is relatively easy using software that HMRC provide via Business Link) to enable paying yourself and other directors, as well as any employees of the company.