This needs a little bit of experience and trial and error tbh. but its best to let the oil sit and settle for at least a few days, so any fat or other crap will sit at the bottom of the containers. Its much easier to avoid tipping it in your filters then.
If anyone on here decides to have a go, Im not an expert, but will willingly give advice if I can.
The forum in the link above has plenty of info, but its arranged in a bit of a chaotic fashion and it can take a bit of digging to find what you need.
As with most things in life! 
However it certainly does give me pause for thought, as someone who spends over £300pcm on diesel! That said, there is some kind of logistics involved in obtaing 50l+ of the stuff per week and disposing of all the waste cans and the residual unusable fat/water/crud (maybe 5% by volume?). Still, probably worth it for near free fuel.
Plus I've got a real hankering for a 1990's volvo - 740 maybe 
Obtaining the amount you need may well be a matter of putting in the initial legwork, and a certain amount of luck as to how many restaurants are in your locality.
I don't like walking in cold and asking,and would probably make my life a bit easier if I did. Some people on the forum have their own little websites for their area and these are the people who often end up with the problem of too much oil.
Legally,a waste transfer note needs to be given to whoever you collect the oil from, but this is a very simple procedure.
The document is downloadable from the forum and can then be copied.
This satisfies the requirement for a paper trail to discourage people tipping down the drain.
Disposal of containers - I squash them down, put them in black bin liners and chuck them in the skip ot my local tip.
Disposal of leftover, fatty stuff can be a little more tricky. In theory it can be put in the waste cooking oil tank at your local tip, if they have one, but most of the tips seem to have a resident "little hitler" who wants to argue about it.
It can be collected up until you have a reasonable quantity and then given to someone who makes biodiesel, if you have someone localish who does this.
It might be crap as WVO, but biodiesel producers will usually still be able to make use of it.
As TB says these cars are often slow by modern standards, although the Turbo,d 2190 on ebay can probably shift along nicely.
Also my first wvo car was a Cavalier 1,7 TD, and it was reasonably quick. In fact it was a hoot to drive, until I killed it dead.
I don't mind driving something slowish like my 190. It just requires a different technique. Get it up to speed and then try hard not to slow down. A bit like driving a truck really.
