>>> Hi, as I don't own the road can I legally clamp?
Nobody can clamp vehicles since the Protection of Freedoms Act 2012 came into effect!
The legal position is outlined in Section 6 (on page 8) here:
http://tinyurl.com/h8az85b
All you can do is to threaten to sue those who obstruct your access for compensation for any, and all, losses suffered by you as a result of their actions (e.g. having to pay for taxis, to and from work, because you couldn't get your car out, lost pay from arriving late at work, etc).