IIRC, just before you exit the Customs area into the Main Terminal (read: landside), there is a small desk for connecting flights where you can recheck your baggage.

One problem with immigrations/customs at DEN is that it's somewhat understaffed, and the LH (A340) and the BA (B777) flights arrive within 40 minutes of each other.

Since you end up landside, you will have to clear security again before making your domestic connection. I haven't flown out of DIA since December, so I can't tell you the current waiting times at security. But, if you don't have a laptop, and just one carry-on, the Express lane is a breeze.

Cheers,
Lawrence