There are pitfalls you need to be aware of. One is 'deemed employment' and IR35, which msy apply if you are a 'managed services' company. Another is corporation tax, which is the tax your company will pay on all profits after allowable expenses. If you intend paying yourself a salary, you will need to operate a PAYE scheme. If you register for VAT, you will have operate that too.
Non of this is complicated, apart from corporation tax, which is very complex, but you might want you give
www.hmrc.gov.uk a few hours of your time.
You need to consider insurance. If you are an employer (which your company will be as you will be be an employee of your Company) you should have employers liability insurance, and you may want to consider Professional Indemnity Insurance.
As a Director of hour Company, you will be subject to company law, and have statory responsibilities. Have a look at
www.companieshouse.gov.uk. The site will also tell you how to set up a company. (Very easy)
www.pcg.org.uk is worth a look too, particularly with regard to IR35.
It isn't just a case of keeping track of expenses, you (or your accountant) are required to keep detailed accounts which have to be submitted to HMRC and Companies House (usually st the same time). Not all expenses are deductable.
With regard to Dividend/salary, salary is a deductable expense, although you will pay tax as part of your company's PAYE scheme. Dividends are not, they are paid after deduction of ct (and have to be declared on your personal tax return, although you get a notional tax allowance for the corporation tax that has been paid)