M8 multispline. Not a torx, not a star headed what not, not an allen bolt or a socket. Some numpties try and sell you the wrong bits if you're not sure what you're after.
If you've ruined them and aren't able to use the M8 tool then I'd suggest a multi sided (not sure the proper name) 12mm socket. The type with the internals like this;
You can tap it on the outside of the head, although it's only really a last resort as it ruins the bolt and i think they're a VW only part. used on everything across the VAG range though so scrappies should have loads. if you try and use a 6 sided socket you probably won't have much luck as it doesn't bite.
You may find it easier to use a couple of extensions to reach. Also, clean the head out with WD40 or scrape it out then tap the multispline in else you stand a good chance of rounding it off.
