I use
www.ukplc.net for my companies and clients' companies where I'm company secretary. It's important that you can not only form the company online but also do all the admin tasks like appoint directors etc but I'm sure all these online companies do that.
It is very useful to have a real person on the end of a phone.
You really don't need an accountant or solicitor to form a company BUT you should take specialist advice if
- you're planning on having a group of companies or the same people owning several companies
- you have a complicated share owning arrrangement
- you plan to issue more shares in future