Well, I can report back... We opted for the Access Ltd Exp in the end, on the basis that it would actually be quicker than doubling back from the Keisei-Ueno station to Asakusa.

It worked a treat. It was the middle of the day, so not overly crowded. The seats are very well padded and defined for bench seating, and there was no problem with luggage - although these trains have decent acceleration, so you need to keep a tight hold on any 'spinner' wheels...

Asakusa station, well, it was three stations, but our section wasn't too bad. Google Maps has a pretty decent multi-level map of the station and area, so it's easy to pinpoint the lift up to street level, and how to get to the Gate hotel - which we also thoroughly enjoyed.