I registered directly with Companies House a few months ago, after consulting an accountant. It was completely straightforward. I don't see any need to use a third party.
The companies I've registered through third parties email me annually with reminders of what needs to be filled when etc, and where I've left a company dormant I can get that filed for a nominal fee and a couple of clicks of a button.
Additionally they often have cash back deals with the banks, so after opening an account I actually ended up with a profit from registering the company (about £5)
This sort of information about the basics is surprisingly hard to find, so this article is particularly refreshing.
Makes me think, I'm sure many people (including me) would be happy to pay to talk (IM) to someone who knows something about this sort of thing. Does this exist as a web service anywhere?
I did find the following from them on finding an accountant: http://www.business.scotland.gov.uk/bdotg/action/layer?r.i=1...