HELP!!!

Today I thought I'd service the car and clear the bits out from my spare room, jacked the car and supported it and removed skid plate, all dry no leaks excellent. Then I shuffled up the the Sump armed with my 8mm allen key and a tub to collect the black gold..... NOPE!!! This plug is TIIIIIGGGHHHTTT!! and the Hex Socket is rounded slightly - I'm sure its been Ugga Dugga'd

I've tried the following

8mm Hex Key
8mm Hex Key - Socket set
Plumbers Grips
Mole Grips
Vice Grips
Stiltsons
Hammering a slightly smaller socket on (19mm)

Nothing has worked, I haven't got any Irwins - but I'm seriously going to get some - which do I need and my torx bits which I think will get them are in Scotland (left on a job)..... 

Any advice - OH and I'm not able to drive the car until Christmas (serving a ban) so I can't exactly take to a garage to be sorted - my plan was to get a service done before I drive it again.

Pictures Attached so you can see what I'm up against.

You could try a bit of heat around the sump, in the hope of that expanding slightly and releasing pressure on the bolt.  I do only mean a bit though, don't want to melt the ally or set fire to the contents!

Yes, if it were me I'd go with heat from a plumbers gas blow torch. Also try tightening it first when hot, it helps to ease the stress on the thread by a fraction of a nano meter, but enough to allow it to break free and then unscrew as normal.

I will give that a shot at some point but the engine was at temp, I did try the tighten trick too but my hex key just slips too, it feels slightly rounded.

Any thought on these?

The sump won't get hot enough just with the engine at temp.

I haven't seen those hex extractors before but they do look a good idea.

Couple of other options - you may find a Torx bit that’s either the right size to fit the hex hole or slightly larger and try forcing that in then undoing the bolt.

Or get a tapered stud extractor set like this 

https://www.screwfix.com/p/hilka-pro-craft-damaged-screw-extractor-set-8-pcs/20084

You’ll have to drill a hole into the bolt for the extractor to start then you screw the extractor in anti-clockwise - as it goes in it gets tighter to the hole and hopefully grips the bolt enough to start loosening it. Look them up on YouTube for more info

Final nuclear solution, grind the head of the bolt away until you can remove enough material for the head to no longer contact the sump, then grip it in some way to remove what remains of the  body of the bolt. You’ll need a new one and sealing washer obviously. 

Hammer and chisel will loosen it. 

all excellent options I'll look into these, Yes I've got a replacement plug and washer, so this on is "sacrificial" just not yet or I'm going to have a load of oil everywhere.

Still open to any other ideas

Get a new sump plug and drill it out