welfare facilities in the workplace

[ste v]

As a mobile worker i sometimes need to travel (never more than 20mins) to one of my employers sites to use the welfare facilities at lunch time - ive now been told that this travel time will now come out of my lunch time and not be classed as work - i.e. my 40min (unpaid) lunch break will be reduced to 25mins if it takes me 15mins to travel to the office to use the welfare facilities ! is this legal ?

[buildersmate]

A grey area, but I reckon 'it depends'.
If the nature of what you do involves specialist protective clothing or hazardous materials such that you need to 'wash and dekit' at the premises prior to taking lunch, it would seem totally unreasonable.
If you are just out and about mobile in everyday clothing and you have some flexibility about when and where you eat your lunch, and you have options about where you can stop for a natural break, it doesn't seem unreasonable because, as an employer, I would be asking 'why do you choose to come back to base for lunch when you are mobile?'.

[ste v]

im a telecoms engineer - i work on underground cables that are generally covered in dirt and grease as well as anything that the rain water carries undergroung i.e oil, diesel. theres also a risk of catching weils disease which can be caught by contact with rat urine ?

[buildersmate]

In those circumstances it would sound right that you should be allowed to return to the base to have a break.
The minimum length of your break by law is 20 minutes (unpaid) and applies when one has had a maximum of 6 hours at work.
However the issue for you here is whether or not you should be paid or unpaid for the travel time. What does your employer regard as your normal place of work? One way to establish this is whether you are paid mileage for the travelling.
There is no specific area of employment law that covers what you are asking here (apart from the need for a break) however you could start a grievance and see where it gets you.