As my Mk3 is going to be scraped.

It has half a tank of diesel, whatââ,¬â,,¢s the best way to drain it please?

Not sure, maybe just disconnect the fuel line from the filter and pump it all out?

Or maybe ask the gaffer at the dump if heââ,¬â,,¢ll buy the fuel off u

If its got an intank pump, disconnect the feed to the front somewhere easy to get to, put a suitable piece of hose over it, and use the pump to pump it out into your container of choice (you might need to find the fuel pump relay and connect a bridge wire across it to get it to run, or you might be lucky and find it runs as soon as the ignition is on but not with the engine started.

Just be aware that when I've tried this on some other cars, you end up with diesel coming out from two places, so you might need a decent length of hose for it.

If there isn't a pump in the tank, your down to something like this on the end of the same hose as above
https://www.ebay.co.uk/itm/12V-60W-Electric-Oil-Fluid-Diesel-Extractor-Transfer-Pump-Motorbike-Car-Siphon/303677778637

Or access the tank via the tank hatch, though that can be a pain to do. Don't try going down the filler, it will be an exercise in frustration as they are usually full of anti-syphoning designs to prevent you being able to do that.

The main thing is definitely do NOT be tempted to drill a hole through the tank and collect it in a bowl, the friction from the drilling could generate heat and set the whole thing on fire, extremely dangerous

I definitely wonââ,¬â,,¢t be doing that. Lol I might need to drive it to the scrap yard yet. Hopefully theyââ,¬â,,¢ll collect.