Not unless your contract says so.
Under the Working Time Directive (which applies to most workers and sets out the minimum standards for working hours), your employer has to offer a break of at least 20 minutes if the working day is longer than six hours, but there is no requirement under the minimum standards for your employer to pay you for this break or to count it towards your working day.
However, your contract of employment may well entitle you to something better, so check your contract terms or staff handbook for more information. Just as most people are paid more than the minimum wage, your employer may well offer more than the absolute minimum on breaks as well.
This will probably be the case if you've got a recognised trade union where you work (as breaks and hours are a priority for unions), so talk to your workplace rep if you have one.
Note that HGV and PSV road transport drivers have better entitlements through the Road Transport (Working Time) Regulations and the Tachograph Regulations that govern driving hours. Other mobile workers in road and rail transport must rely on a rather vague standard, in that they must receive 'adequate rest'.
The regulations are also stricter for workers aged 16 and 17, who must receive a break of at least 30 minutes if they work for 4.5 hours or longer.