If your liner is not long enough for your installation there will undoubtedly be delay and disappointment (plus the additional cost of a correctly sized due liner). Adding an extra metre (or two) - will help ensure your installation goes ahead without delay and could save you far more than the small additional cost.
If your liner is not long enough for your installation there will undoubtedly be delays and disappointment (plus the additional cost of a correctly sized flue liner). Adding an extra metre (or two) - will help ensure your installation goes ahead without delay and could save you far more than the small additional cost.