At long last, I got my "new to me" camera bag. It is a Crumpler "Three Seven Daily". It easily accommodates my EM-1, with battery grip & 12-40 lens attached. Next to the camera is my 40-150 lens, and in the slot behind is my ElitePad 10" tablet.
There are plenty of additional pockets for the usual array of camera nik-naks.
The whole padded camera section can be removed, and the Crumpler can be used as a messenger bag.
Very pleased with my purchase, at £25 incl. delivery.