Damn Gav, what a shame.
If you really think the bubbles are the top veneer of the ply lifting, then I'm not sure you should try sanding them back, as I assume you will end up sanding through the top veneer and who knows what you will find underneath. I tried to sand lifting veneer on a table once. Totally ruined the table. If they are really that noticable then you may need to sand back the whole sides and put some sort of solid colour on the sides so the patches can't be seen.
Or are they small enough so you can live with them?