No chance of being let into the SEN - and quite rightly so IMHO.
SEN lounges are for SEN pax, *G pax and F pax. That is enough already.
I am not sure about the Business Lounge at DUS. Do they have showers there too ? (They were rebuilding there for quite some time but I have not been in there). With the inter-continental route expansion ex-DUS there might be showers there now too ??