Many Thanks Trailer Guy
Being struggling all afternoon trying to fit some new Knott Avonride brake shoes. In the end googled YouTube video and found a fantastic video on how to do this by a Trailer Guy. First I was fitting the springs outside in, instead of inside out. Then I had fitted the short spring at the top instead of at the bottom. Had not realized there were two sizes of springs.
Thirdly and perhaps most importantly Trailer Guy suggested checked how freely the brake cable was. Mine was seized so no wonder I had problems.
Luckily as I am in France I had spare hubs with bearings, new brake pads and new cables .
I will get the old hubs replaced with new bearings and spare cables and brake pads ready for the future.
What is worrying is that the Snipe trailer is only two years old with flushing kit and yet already the brake shoes have rusted off.