I tried to get a group together on one of these a few moons ago. My research found the following:
1. Eye watering oil consumption, normal range is anything from 1-3 litres/hour
2. The undercarriage is not as strong as it looks and there is at least one Argus in the UK that, even after having it's wheels wiped off, didn't have the mod included when it was rebuilt. (It was reviewed in Pilot 5-6 years ago)
3. No faster in the cruise than an Auster
Good luck they are lovely aircraft.
If you like the looks you could also go for the mini-Argus, the Auster Autocar, which, with a Gipsy engine, has all the performance and a reasonable spares supply. Not quite so much room inside though!!