My fuel lines are the hard, shiny plastic type as well except I don't recall them being very thin. I have not had any issues running B99 in them. I did have a leak in the braided fabric covered return lines but no issues after replacing them.
If the seals in the fuel and lift pump are Viton (not rubber) there should be no issue with them. Does anyone know if there are rubber components inside the lift and fuel pumps? It would be good to confirm this. I haven't had any issues with the pumps either.
Land Rovers. A loosely associated collection of parts, generally traveling in the same direction.