One additional thing: If you're married make sure your spouse is a director of the company as well (especially if they're not working). You can be hugely tax efficient in this manner and can extract nearly £80k per year from the company with no personal tax to pay (there will still be corporation tax to pay on profits).
There might be some pretty good small accountancy firms around that will cost a LOT less than these fancy online firms, so do check around locally, or asks for recommendations -- I think it's worth it.
I have heard good things about Crunch's system but some mixed things about the quality of their advice and how pro-active they are - any other feedback on them or others?
The point about the registered address and fraud is a real one, someone I worked with had this happen to them - will Crunch act as the service address as well as the registered address?
Having said that, just about everything is automated or part of their software now and I haven't had to speak to anyone there since last summer. Maybe their service hasn't gotten any worse, it's just become less personal.
If you speak to your account controller, they'll be able to set you up a dummy account to see if you like it - my understanding is that this would replace the monthly submissions of expenses and invoices, and give you a better real time view of your profit/loss, but you should still get the same level of service and attention paid to your account and it costs no extra. I'm still waiting for confirmation of all that (my worry being that I could make a mistake and it wouldn't get spotted, whereas it would with a monthly submission to a human) and for my account to be set up, so I can't comment any more on it, but it's definitely worth a look!
Tax planning really should not be a reason to go contracting. You can get more money by moving to another permanent job elsewhere.
Valid reasons to me for going contracting would be to remain technical, to continue learning new technologies, to avoid permie politics and appraisals (which is why I contract)..