I'm a bit confused by your usage of the phrase "several SWU's."

Remember that LH upgrades are for STAND BY at the gate or check-in only. So, you say your transatlantic sector was with UA, and it was upgraded with one SWU. If you wanted to upgrade FRA-wherever on LH, it would be standby at the gate. Also note on LH it is PER SECTOR, so you could not use the SWU you upgraded the transatlantic sector with to also upgrade the next sector (only on UA).

At any rate you can use UA SWU's on any LH flight on a stand by basis.

(most people though would, I believe, consider using a SWU to upgrade an intra-european sector a great waste, but each to their own )

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RichardMEL, UA 1K
A Star Alliance Member.