I have finally got the fibre behind the gib and am now waiting for Chorus to install next week. The process was not straightforward for me. My regular electrician said he could not do the job so I advertised the job on Builderscrack. I got a couple of responses and chose one. He sent somebody round to look at the job and said he would have to cut around either side of a dwang in the wall. He said he would make good the gib for plastering and painting. We agreed a time for the job to be done. He then changed the time and sent somebody else who looked at the job and said he could draw the fibre behind the gib using the same path as the telephone wire. He argued that holes through dwangs are usually 25mm in width and that there would be room for two wires. He and an assistant who was in the roof completed the job in 15 mins or so.

From this I think that if anybody else needs this done they should ask around until they find somebody who had done it before. The man who completed the job said he had done far harder ones using lengths of chain to find the holes to get the wire through.