Thanks, bearcub. That's really informative and useful.

Set up a limited company many years ago, no need to go to any expense its a simple exercise with Companies House.
I have £10m PI its a requirement from many clients and costs very little, I shop around but always end up with Hiscox.
Have 3 months living expenses and what you will expect to pay on travel and hotel fees for your work in reserve. Remember if you are on 60 days payment from invoice it will be the period of time you worked plus invoice submittal 60 days.
You are a small limited company so you may have to accept the term of the company you are engaged with.
I run payroll every month, I used to pay myself a decent wage now I pay myself £9,100 a year plus dividends to avoid employer and employee NI. Yes i have paid my full whack of Ni contributions over the years.
Don't worry its gets easier as you get experience. I have never regretted a day since setting up my limited company, wish I had done it sooner but that's hindsight.

Unless we know what actual field your in , the responses are just general stuff. I have never needed PI insurance ,but i do need PL and EL . I have never used or needed a solicitor. You can dictate whatever terms you want for payment, however that may or may not happen in real life. Will just depend on your customers. An Accountant is a must for your year end accounts. I have always had someone working part time, putting through invoices doing statements chasing money etc. It would be a very long day if you were trying to do it all. The unpaid holidays are another factor to take into account. Its funny my pals say if we are out for a few beers, just take the day off you are your own boss. Yes i am, however i now have more of them than ever. They are just called clients

Is your job in any way regulated ?
If what are their requirements ?
PI is key.
May also want to consider Keyman insurance
Do not forget - Income protection (when you get sick and ill)
Also do not forget pension provisions.
Consider running all expenses through the company.
Will you breach the VAT threshold, if so you need to register and set up for VAT.
The key initially will be to work closely with an accountant.
You do not not need a specialist accountant - as simple basic one or even an online one such as Taxscouts can help at minimal cost.
The opening of business bank accounts is becoming increasingly harder as times go by - so may want to get started on this - for this you need to think about invoicing and payment methods (cheque, Bacs, Cards etc).
Also what does you trading activity look like - is it a lot of small ticket invoices - or is it a few large amount low volume payments - make a difference for recording and banking, chasing. How do you charge, some upfront, some part way through, or all at the end - are the payments recurring - do you need someone to chase payments.
Also consider premises - will it be home (be very careful about apportioning costs and expenses from main residence as it can lead to CGT on your main home in the future if not done correctly) - perhaps better to pay for a virtual or postal office address - very competitive nowadays. (companies house will need the directors address - which cannot be the virtual to send their legal documents)
Just a few considerations - plenty more
However do not be put off, is sounds complicated but it is not necessarily - you just need to think it through.

Deleted - repeated another poster comment on VAT !