Strange as it may seem, there are species which mine the bark of young oak trees. They are found mining the smooth bark of young saplings, usually ones that are about 3 - 5 inches across at chest height. Apparently they can also mine branches of larger oaks but I have never seen this myself.
Until a couple of years ago, identification was easy; it was Ectoedemia atrifrontella. However E. longicaudella has now been found in Britain and the mines are inseparable. The only way to resolve identification then is to coppice the oak and breed through the adult. As most records in the past have been of mines and therefore can now only be referred to one or the other, we have very little knowledge of the distribution of either species and obtaining definitive records is very worthwhile.
Many of the mines I have seen have been on scrubby oaks on heathland so site managers may be happy for you to contribute some scrub clearance!