It might be a stable door behind a horse, but in case this a/c is used again in UK airspace, or not, a phone call to UK CAA might be appropriate. You'd feel uncomfortable if something did happen with this a/c due to your perceived problem. There are operators who survive by supplying a/c & crew to fill holes in peak season and last minute operations as this. Standards might not be up to the regular airlines and old equipment is not uncommon.