before (or after) you spend any money see if business link can give you vouchers for free advice
http://www.mybusinesslink.co.uk/
As an aside, I formed my own limited company last year (via madesimplegroup.com) - but mine was very simple and as it turned out wasn't needed as I found permanent employment but I still used businesslink to gain a £250 voucher session with an accountant to discuss the detail.
The cost for setting up the company was approx £35 and £10 recently to de-register it. I will still need to do my tax return as a director (of a company that never traded) but those forms and online IR have never caused me any issues.
I bought the pdf version of a book in Staples that has all the business forms and minutes you need, plus bought the online share certificates form templates. I used Alliance and Leicester for 2 years free banking so in all the total cost to me of setting up and closing the business has been approx £90 including web address and emails.
As a woody i even created the legally required sign at the head office (home) - but for more money I could have had the head office somewhere in london or with an accountant office.
I only set up the ltd company to assist in some contracting work but it never materialised and I took a permanent position, hence why i deregistered.
the most valuable aspect of the whole process was the business link voucher that gave me 2 hours with an accountant - if I had proceeded their advice would have been critical. The vouchers can be used for anything (e.g creating a business plan)
I may not have followed the best path, but i used advice from others that had been successful. If you intend to employ staff then no doubt the 'web prepackaged' route is more risky
Dave