Okay… the confusion begins! 
My username contractdriver is just that… a username.
I’ve never had a contract for driving work in my life.
Many years ago, before agencys became ‘professional’ I hired my driving services out to owner drivers and haulage companys as a ‘Casual’ driver either on a day rate, week rate or trip rate if i was doing international work.
Over the years things have changed and about 8 years ago i formed a Ltd Company (as a haulage company) and registered it for VAT as a haulage company and all my work comes from agencies.
The company pays me a fixed weekly wage of which i pay tax and national insurance on every week regardless… if i work 1 day, 3 days, 6 days or take 2 weeks holiday i still get paid every week.
I claim my subsistence expenses from as agreed by hmrc, digs money £33.85 per day, meal allowance of £25 per day (company agreed p11dx with hmrc) and other incidental expenses i am allowed which add up to about £7 without having to provide recipts.
Mobile phone, internet, laptop etc are all bought by and provided by the company.
I run my agency driver services limited company in the same way any limited company is run… i legally have to do this, the money the company has earned is the companies… not mine, if i just take a ‘few quid’ for myself… i’m technically stealing money from the company.
Corporation tax is paid on any profits the company makes and employers national insurance is paid on my wages by the company.
I will be employed for as long as my company exists… and will never lose my job!
If a limited company pays a wage, the recipient is an employee regardless of your ‘position’ in the company… if you call yourself a managing director, director, cleaner or whatever.
To claim lorry drivers subsistence you must be employed as a lorry driver!
I’m ‘just’ a driver… not an accountant… and i might be talking bollox… anyone thinking of going ltd needs to speak to an accountant. 
Col
P.s. i’ve never, ever filled a self assesment out… because i’m not self employed.