I have a 89 525i which I'm in the process of chaning out the fuel lines. On the supply and return in the engine bay I needed a little over 4 feet for each line, supply and return.
From the Tank to the filter and such under the car and in the rear i haven't changed those yet, I ordered more line for that. So that should give you alteast the engine compartment idea.
All the hose on my car is 8mm which I have ordered from pelican parts, they sell it per meter at a reasonable price. Also if the hose clamps look rusted, spend a few $$ and replace them all with good quality EFI clamps.