As above. Just make sure it doesn't get blown away or whatever. Has to be there and seen when the site is inspected or you'll have to start all over again.
A bit late, but if anyone else has the same problem.
I was out for a walk earlier, and noticed my neighbours had a planning notice up. Steel post, metal backed sign with a perspex front. Very professional looking. I had to check who put it up - http://www.sitenotices.com
No prices on their website, but here's another company offering same service for 100 in Dublin, and 150 in neighbouring counties https://www.psni.ie