As a youngster, I watched this one with my parents. As the credits rolled, my mother shook her head and proclaimed, "That was a load of rubbish!" My father concurred. 'The Swedish Tiger' has a reputation as the only truly bad episode of 'Upstairs, Downstairs' and it is easy to see why. It is certainly the least representative of the series as a whole.
'Upstairs, Downstairs' generally made a good job of mixing naturalistic humour with serious drama but 'The Swedish Tiger' is pure light comedy. As such, it is well done: with clever, witty, deliberately-artificial dialogue. James, Elizabeth, Sarah and Edward are the only series regulars in it and they, along with the guest cast (which includes the genuinely-Swedish Sven-Bertil Taube), handle the sophisticated shenanigans with aplomb.
On the one hand, the tone of the production is egregiously out of kilter with that of the rest of the series. On the other hand, it surely deserves some credit for daring to be so boldly different. I can see why many people disliked this episode - but I thoroughly enjoyed it.