I operate a chauffeur company and some of my vehicles are private hire licensed. I am VAT registered as my turnover tales me over the VAT threshold. The following is taken from HM Revenue & Customs website:

1.2 What is liable to VAT?
The fares you charge to your passengers for taxi or private hire journeys are liable to VAT at the standard rate. This also includes any additional charges you may make such as for:

baggage or
waiting time.
Other sources of income liable to VAT may include:

referral fees received from another taxi firm (where, for example, you have passed business on to them)
charges for supplying fuel or the rental of vehicles and/or radios to drivers and
administration charges to customers (for example where you provide them with periodic details of the journeys they have made).
On the other hand, tips or gratuities that are voluntarily given by passengers are not regarded as payment for a supply and are therefore outside the scope of VAT.

Where your charges are VAT inclusive, you can work out the VAT element by multiplying the fare, including any extras, by the VAT fraction. You can find out more about the VAT fraction in Notice 700 The VAT Guide