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Thank you Alan, My only thoughts are that if a visitor needed to contact the company the first place they would look is the main navigation and if there is none they would be forced to select an option to continue, 'residential' or 'commercial' which may confuse or annoy site visitors.

You're welcome. Yes, that's right.  When it comes to catering for duplicate content issues, there will usually be a page (such as the one with the Canonical tag) that won't be best placed for search. Inbound links, for example, will be best pointed to the main page, such as your main Woodside page. This will be the page to focus the SEO on for that particular location. Regards Simon