Here's what the net says.
Under a new European Union Directive, professional bus, coach and lorry drivers need to hold a Driver CPC in addition to a vocational driving licence. Any drivers of lorries over 3.5 tonnes and minibuses with 9 seats or more must obtain a Driver CPC.
New drivers obtain their Driver CPC by passing a series of initial qualification tests - theory and practical. This must then be followed by 35 hours of periodic training every five years if they want to keep their Driver CPC after that period.
Bus and coach drivers who hold a relevant vocational licence gained before 10 September 2008, and lorry drivers who obtained their licence before 10 September 2009, do not need to take the initial qualification. This is because they are deemed to hold 'acquired rights'. However, they will have to complete periodic training to keep their Driver CPC.
Driver CPC is valid for five years. New drivers who have qualified via the initial qualification route will receive a Driver Qualification Card (DQC), which they can show as proof that they hold Driver CPC. Existing drivers will receive their DQC when they have completed their 35 hours of periodic training. Their DQC will be valid till 9 September 2018 for PCV drivers and 9 September 2019 for LGV drivers. Holders of both licences will be covered by one DQC and only need to take 35 hours of periodic training in five years once. Also holders of both licences will have their DQC valid for all groups (HGV & PSV) till 9 September 2019
http://en.wikipedia.org/wiki/Driver_CPC