Set up for the tax man
Once your company has been registered with Companies House you will then need to register for taxes in the UK. HMRC should automatically send you your Corporation Tax registration but if they don't it is important to remember that you will need to register for this as soon as you start trading in the UK.
You will need to think about when will be the right time to register for VAT in the UK. It may be the case that you should register for VAT in the UK before you incorporate your company in the UK if you have already been making sales to UK customers. Once your sales in the UK hit the VAT threshold (currently turnover of £85,000) then you will need to register automatically.
If you have UK employees then you will need to register your PAYE scheme in the UK which will allow you to pay your employees and deduct the correct taxes and social security to be paid across to HMRC.