Did the GU for CLH (Lufthansa Cityline) in 2008. On that day we had no mental arithmetic but did have a simple applied maths test. I think we did have pen and paper for that.
As far as I know, DLR put together batches of test for each client. Can't imagine LHI will be significantly different to any other within the group and a pass at one is normally recognised by the other companies within LH (Sadly the same goes for a fail too!).
Just in case anyone has failed to get the message, the DLR is a ONCE ONLY test for ready entries (although, if you fail the BU you can have one other try as a ready entry).
KT