I wouldn't compromise on quality when it comes to head gaskets. If you do, you'll only have to do the job again next year. Why have a Mercedes-Benz CL600, arguably the finest Mercedes-Benz available, and then seek to skimp on parts?
Try your local motor factors.....though don't get your hopes up! Recently did my 450 SEL 6.9 and the gaskets were Mercedes main dealer only at £250 per side!