I worked on a couple of these way back in the 80s. They were dogs then and I am surprised there are still any around. FOPR stands for Fork, Ordinary which means standard, Petrol, Rider which means you sit on it. 6 is just a model number and 2.0 is 2 ton. It is probably a Perkins engine, maybe a G4 but the memory is dim. It is probably a Kirkstall axle with hub reduction and they were fragile. I cannot remember where the hydraulic pump is driven from, I suppose you could check it has one and that there is oil in the system. After that you would look to see if there is any oil circulating in the system perhaps at the tank return. Again I forget which control valve is on these but other Lansing Bagnalls of that era had a control valve that used to experience relief valve issues. If it is the same there is a sintered brass disc at the bottom of the valve held by a circlip. Careful dismantling and cleaning sometimes got the valve going again but often they needed replacement of the whole relief valve.