I found this movie on a TV channel a few years ago and really enjoyed it. It's good to own the DVD now, which also has a couple of extras...including a small featurette.
On first appearances, yes, it looks very "budget movie", with dodgy sets, dodgy script, shakey acting in places and a wobbly storyline...BUT it is STILL a good movie to watch.
It has all the elements of undercover intelligence within Germany in WW2, with a light love story over the top of it. Add into the equation that Griffiths' character is also half-Jewish, it gives a little more grit to the story. Particular good points include Joely Richardson's performance; as good a woman semi-villain as you'll get anywhere. A good strong performance by Liam Neeson as a German General and also the fact John Gielgud plays a small part gives the movie some credit too.
It's a very simple story, slightly predictable, but you'll find the movie much better and more enjoyable than you think.