A very helpful comment to my last past on the history of Floyd Road has confirmed that their used to be a railway, or a tramway as a number of documents refer to it as, running from the sandpits under where the football stadium is down to the river. The footpath under the railway on Ransom Road with it's arches is indeed the course it followed. I'm tempted to nip down there with a tape measure at some point to check it's width out, I'm not at all sure it's big enough for a standard gauge track.
The tramway was built by Lewis Glenton who got permission for it in 1840, it was certainly there in 1852 as it's referred to when giving the location for a garden in another document. That reference also confirms that the pub on the corner of Church Lane and Woolwich Road was known as the Antigallican (or Anti-Gallican, making it's anti French meaning very apparent) at that time too.
There appears to have been some legal problems building the tramway, there was a court case between Sir Thomas Maryon Wilson (whose family owned much of the land around here) and the Reverand of the parish Church and Lewis Glenton in 1840 or 1841. The Reverand might have been involved because the case refers to the tramway being built over "Glebe land", which is Church owned land that is rented out. So maybe the Church owned the land, Lewis Glenton rented it and built the tramway along it. I wonder what Sir Thomas' problem was?
Anyway thanks very much to the anonymous poster, if anyone does know anymore about the tramway please pass it on.
Here's some information that I've managed to find with a quick bit of googling....
Greenwich Industrial History Society
The National Archives