There were some from another airport not East Mids in the sky around you at the time....... you can select a time and watch them inflight here... there is a tracking service you can run for East Mids and you just sort of come on the bottom of the map
they do not appear to be from East Mids as nothing at that time was coming from or going too it...... the yellow ones are from another Airport
http://www.eastmidlandsairport.com/cms/173/webtrak.html