Thanks for the thoughts. Yes, I thought 4 weeks might be nearer the mark. However the most important thing is making a full recovery so I'll take the doctors advice.
I should be clear I'm not paid to fly - I do it for fun, in a glider, so probably go up (& down) faster than most other things so rate of change of pressure (which I imagine is the real problem) is bigger. As I'm not an instructor my medical is based on my fitness to drive, and I was advised not to for 2 weeks after the first discharge but that was mostly in case I had to do an emergency stop.
I've no idea what kind of chest drain it was - there was a thinner tube coming out of my chest which was joined to a very robust & uncrushable silicon tube just over 1cm diameter which went down to the collecting vessel.
Certainly I'm not ready to fly yet as I'm short of breath and would run into hypoxia much more quickly than normal. Also I'm not yet ready to rig my glider - it's not the heaviest, but it is heavy - but maybe playing the 'poorly sick' card, or finding a load of visitors at the club would do that. However I'll have to do some dual flying and also my annual checks before I can fly solo again.
I'm also so glad to have escaped hospital again. A lot of what goes on would be considered torture if applied to the general populace - the noise, the lack of sleep, the regimentation, the food....