Thanks again for the advice folks. As it was a bright evening I went and tried it out tonight. Newbridge end is quite easy to find once you know where it is. Coming from the west, as you come down the ramp off the bridge over the M9, you basically turn to the right, back on yourself, and the path dips under the bridge. It's pretty narrow to begin with, but soon widens. Surface is firm enough though I would imagine after rain it can probably get a bit muddy. Probably wouldn't fancy it on anything narrower that 25mm tyres except after a long dry spell.
I followed it through Kirkliston which was far more pleasant than the road alternative at that time of the evening. There's no signage to be seen anywhere, so you have to guess which way to go at times, but it's all pretty obvious.
As my destination was in town I dropped back onto the Kirliston-Cramond road where the path crosses it and starts heading to Dalmeny. The ramp down to the road is quite muddy and rutted, but passable. Most of the motorised traffic on that road is going the other way, so this is a pretty good way into town if you're heading for the north side, linking up with NCN1 at Cramond Brig and then into the NEPN.
Links to the canal from the Newbridge end?
1) use the footbridge in Ratho Station, then station Road to link onto Baird Road to Ratho, where you can pick up the canal by the Bridge Inn.
2)Use the bridge over the M9 then follow the cycle path alongside the A89 westbound. Just before the big brick railway viaduct there's a wee lane (Birdsmill?) running off to the left and under the viaduct. Follow this, ignoring a left turn for Birdsmill, until you get to the Astor pub, take a left at a Give Way to go over the M8 and under a railway bridge to reach the canal.
3)As (2) but stick with the cyclepath by the A89 until you get to the right turn for Winchburgh. This jinks right over the railway line, then runs parallel to it, before turning left, back across the railway and shortly after, the canal.